CBSE – Grade 10 – Science – Ch 02 – QA

Questions & Answers

CBSE - Grade - 10

Subject: Science

Chapter - 02 - Acids, Bases and Salts

Types of Questions

MCQ

  1. General Properties of Acids and Bases

Q1. Which of the following is a property of acids?
 (a) Bitter taste
 (b) Soapy touch
 (c) Sour taste
 (d) Turns red litmus blue

 Answer: (c) Sour taste

Q2. Which of these is a weak acid?
 (a) Hydrochloric acid
 (b) Sulfuric acid
 (c) Acetic acid
 (d) Nitric acid

 Answer: (c) Acetic acid

Q3. Bases are substances that release:
 (a) H⁺ ions
 (b) OH⁻ ions
 (c) CO₂ gas
 (d) Cl⁻ ions

 Answer: (b) OH⁻ ions

Q4. Which of the following is NOT a base?
 (a) NaOH
 (b) NH₄OH
 (c) H₂SO₄
 (d) KOH

 Answer: (c) H₂SO₄

Q5. What happens when an acid reacts with a metal?
 (a) Oxygen gas is released
 (b) Hydrogen gas is released
 (c) Water is formed
 (d) Carbon dioxide is released

 Answer: (b) Hydrogen gas is released


  1. Indicators and pH Scale

Q6. What is the color of phenolphthalein in an acidic solution?
 (a) Pink
 (b) Colorless
 (c) Blue
 (d) Yellow

 Answer: (b) Colorless

Q7. What is the pH of pure water?
 (a) 0
 (b) 5
 (c) 7
 (d) 10

 Answer: (c) 7

Q8. A solution has a pH of 3. It is:
 (a) Neutral
 (b) Weakly acidic
 (c) Strongly acidic
 (d) Basic

 Answer: (c) Strongly acidic

Q9. The pH value of a strong base is:
 (a) Less than 7
 (b) Exactly 7
 (c) More than 7
 (d) Cannot be determined

 Answer: (c) More than 7

Q10. If a solution turns red litmus blue, its pH is likely to be:
 (a) 1
 (b) 5
 (c) 7
 (d) 10

 Answer: (d) 10



  1. Chemical Reactions of Acids and Bases

Q11. What is formed when an acid reacts with a metal carbonate?
 (a) Hydrogen gas
 (b) Carbon dioxide gas
 (c) Oxygen gas
 (d) Ammonia gas

 Answer: (b) Carbon dioxide gas

Q12. Which equation represents neutralization?
 (a) HCl + NaOH → NaCl + H₂O
 (b) Zn + HCl → ZnCl₂ + H₂
 (c) Na₂CO₃ + HCl → NaCl + H₂O + CO₂
 (d) Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

 Answer: (a) HCl + NaOH → NaCl + H₂O

Q13. What happens when carbon dioxide is passed through lime water?
 (a) Lime water turns milky
 (b) A pungent smell is produced
 (c) The solution turns red
 (d) It remains clear

 Answer: (a) Lime water turns milky

Q14. The reaction between an acid and a base is called:
 (a) Displacement reaction
 (b) Decomposition reaction
 (c) Neutralization reaction
 (d) Redox reaction

 Answer: (c) Neutralization reaction

Q15. What gas is released when acids react with metals?
 (a) Oxygen
 (b) Hydrogen
 (c) Nitrogen
 (d) Chlorine

 Answer: (b) Hydrogen



  1. Common Salts and Their Uses

Q16. What is the common name of NaCl?
 (a) Baking soda
 (b) Common salt
 (c) Washing soda
 (d) Bleaching powder

 Answer: (b) Common salt

Q17. Which salt is used to remove hardness of water?
 (a) Baking soda
 (b) Washing soda
 (c) Bleaching powder
 (d) Table salt

 Answer: (b) Washing soda

Q18. Which chemical is used in fire extinguishers?
 (a) NaCl
 (b) NaHCO₃
 (c) CaOCl₂
 (d) NaOH

 Answer: (b) NaHCO₃

Q19. Which of the following salts is used in making glass?
 (a) Na₂CO₃
 (b) NaCl
 (c) NH₄Cl
 (d) CaCl₂

 Answer: (a) Na₂CO₃

Q20. What is the chemical name of bleaching powder?
 (a) Sodium chloride
 (b) Calcium oxychloride
 (c) Sodium bicarbonate
 (d) Calcium carbonate

 Answer: (b) Calcium oxychloride




  1. Application-Based Questions

Q21. Why should curd not be stored in metal containers?
 (a) It reacts with metal
 (b) It changes color
 (c) It loses nutrients
 (d) It becomes solid

 Answer: (a) It reacts with metal

Q22. Which gas is produced when NaHCO₃ is heated?
 (a) O₂
 (b) CO₂
 (c) H₂
 (d) Cl₂

 Answer: (b) CO₂

Q23. What is the role of acids in our stomach?
 (a) Help in digestion
 (b) Help in blood clotting
 (c) Increase pH
 (d) Help in respiration

 Answer: (a) Help in digestion

Q24. What is the effect of acid rain on aquatic life?
 (a) No effect
 (b) Increases oxygen levels
 (c) Decreases pH, harming aquatic organisms
 (d) Enhances plant growth

 Answer: (c) Decreases pH, harming aquatic organisms

Q25. What is the chemical formula of Plaster of Paris?
 (a) CaSO₄.2H₂O
 (b) CaSO₄.½H₂O
 (c) Na₂SO₄
 (d) Ca(OH)₂

 Answer: (b) CaSO₄.½H₂O




  1. Water of Crystallization & Plaster of Paris

Q26. What is water of crystallization?
 (a) The amount of water added to a solution
 (b) Water molecules present in a salt’s structure
 (c) Water that reacts with acids
 (d) Water obtained after a reaction

 Answer: (b) Water molecules present in a salt’s structure

Q27. What happens when blue copper sulfate (CuSO₄.5H₂O) is heated?
 (a) It turns white
 (b) It turns black
 (c) It dissolves in water
 (d) It forms a gas

 Answer: (a) It turns white

Q28. Which of the following salts contains water of crystallization?
 (a) NaCl
 (b) CuSO₄.5H₂O
 (c) Na₂CO₃
 (d) NaHCO₃

 Answer: (b) CuSO₄.5H₂O

Q29. How is Plaster of Paris (POP) obtained?
 (a) By heating gypsum at 373K
 (b) By dissolving CaCO₃ in acid
 (c) By reacting lime with water
 (d) By mixing sodium carbonate with acid

 Answer: (a) By heating gypsum at 373K

Q30. What happens when Plaster of Paris is mixed with water?
 (a) It hardens into gypsum
 (b) It turns blue
 (c) It dissolves completely
 (d) It turns acidic

 Answer: (a) It hardens into gypsum




  1. Importance of pH in Everyday Life

Q31. What is the pH range of human blood?
 (a) 1-2
 (b) 4-5
 (c) 7.35-7.45
 (d) 9-10

 Answer: (c) 7.35-7.45

Q32. What is the effect of acid rain on soil?
 (a) Increases soil fertility
 (b) Decreases soil pH
 (c) Converts soil into base
 (d) No effect

 Answer: (b) Decreases soil pH

Q33. What should be added to soil if it becomes too acidic?
 (a) Common salt
 (b) Quick lime (CaO)
 (c) Vinegar
 (d) Sugar

 Answer: (b) Quick lime (CaO)

Q34. Which substance helps neutralize stomach acid?
 (a) NaHCO₃ (Baking soda)
 (b) NaCl (Common salt)
 (c) CaOCl₂ (Bleaching powder)
 (d) CuSO₄ (Copper sulfate)

 Answer: (a) NaHCO₃ (Baking soda)

Q35. Tooth enamel starts decaying when the pH of the mouth falls below:
 (a) 7
 (b) 5.5
 (c) 4
 (d) 3

 Answer: (b) 5.5




  1. Industrial Chemicals from Common Salt

Q36. What is the process used to obtain sodium hydroxide from common salt?
 (a) Neutralization
 (b) Chlor-alkali process
 (c) Electrolysis of water
 (d) Decomposition reaction

 Answer: (b) Chlor-alkali process

Q37. What are the main products of the chlor-alkali process?
 (a) NaOH, Cl₂, H₂
 (b) NaOH, CO₂, H₂O
 (c) NaCl, H₂, O₂
 (d) NaHCO₃, H₂, CO₂

 Answer: (a) NaOH, Cl₂, H₂

Q38. Which chemical is used in disinfecting drinking water?
 (a) Baking soda
 (b) Bleaching powder
 (c) Washing soda
 (d) Vinegar

 Answer: (b) Bleaching powder

Q39. Which industrial chemical is used in making soaps and detergents?
 (a) NaOH (Sodium hydroxide)
 (b) NaCl (Common salt)
 (c) NaHCO₃ (Baking soda)
 (d) H₂SO₄ (Sulfuric acid)

 Answer: (a) NaOH (Sodium hydroxide)

Q40. Washing soda is chemically known as:
 (a) Sodium bicarbonate
 (b) Sodium carbonate decahydrate
 (c) Calcium oxychloride
 (d) Sodium chloride

 Answer: (b) Sodium carbonate decahydrate




  1. Miscellaneous Questions

Q41. Which of the following substances is used to manufacture glass?
 (a) NaHCO₃
 (b) Na₂CO₃
 (c) CaOCl₂
 (d) NaCl

 Answer: (b) Na₂CO₃

Q42. Which gas is released when acids react with bicarbonates?
 (a) Hydrogen
 (b) Oxygen
 (c) Carbon dioxide
 (d) Chlorine

 Answer: (c) Carbon dioxide

Q43. Which of these acids is present in ant stings?
 (a) Acetic acid
 (b) Oxalic acid
 (c) Citric acid
 (d) Methanoic acid

 Answer: (d) Methanoic acid

Q44. Why does baking soda help in cooking?
 (a) It acts as a sweetener
 (b) It produces CO₂, making food soft and fluffy
 (c) It changes the taste of food
 (d) It makes food hard

 Answer: (b) It produces CO₂, making food soft and fluffy

Q45. What is the pH of a strong acid like hydrochloric acid (HCl)?
 (a) 0-3
 (b) 4-5
 (c) 6-7
 (d) 8-10

 Answer: (a) 0-3

Q46. Which of the following acids is present in tomatoes?
 (a) Citric acid
 (b) Oxalic acid
 (c) Acetic acid
 (d) Tartaric acid

 Answer: (b) Oxalic acid

Q47. What happens when excess carbon dioxide is passed through lime water?
 (a) Solution turns milky
 (b) Milky solution clears up
 (c) Solution turns red
 (d) No change

 Answer: (b) Milky solution clears up

Q48. Which of the following salts is used as an antacid?
 (a) Na₂CO₃
 (b) NaCl
 (c) NaHCO₃
 (d) CaOCl₂

 Answer: (c) NaHCO₃

Q49. Which acid is present in vinegar?
 (a) Hydrochloric acid
 (b) Acetic acid
 (c) Nitric acid
 (d) Sulfuric acid

 Answer: (b) Acetic acid

Q50. Which compound is used to make soft water from hard water?
 (a) Baking soda
 (b) Washing soda
 (c) Vinegar
 (d) Bleaching powder

 Answer: (b) Washing soda

Fill in the Blanks

General Properties of Acids and Bases

  1. Acids have a ______ taste, while bases have a ______ taste.
      Answer: sour, bitter


  2. Acids turn ______ litmus red, while bases turn ______ litmus blue.
      Answer: blue, red


  3. The chemical formula of hydrochloric acid is ______.
      Answer: HCl


  4. Bases feel ______ to the touch due to their reaction with oils on the skin.
      Answer: soapy


  5. The chemical formula of sodium hydroxide is ______.
      Answer: NaOH


  6. The acid present in lemons is ______ acid.
      Answer: citric


  7. The acid present in vinegar is ______ acid.
      Answer: acetic


  8. The base used in soap making is ______.
      Answer: sodium hydroxide (NaOH)


  9. ______ acid is used in car batteries.
      Answer: Sulfuric


  10. The chemical name of slaked lime is ______.
      Answer: calcium hydroxide (Ca(OH)₂)


Indicators and pH Scale

  1. The pH scale ranges from ______ to ______.
     Answer: 0, 14


  2. A solution with a pH of 7 is ______.
     Answer: neutral


  3. A solution with a pH less than 7 is ______, and a solution with a pH greater than 7 is ______.
     Answer: acidic, basic


  4. The universal indicator shows different ______ at different pH values.
     Answer: colors


  5. The indicator extracted from lichen is called ______.
     Answer: litmus


  6. Phenolphthalein remains ______ in acidic solutions and turns ______ in basic solutions.
     Answer: colorless, pink


  7. The acid present in our stomach is ______ acid.
     Answer: hydrochloric (HCl)


  8. Tooth enamel starts to decay if the pH of the mouth falls below ______.
     Answer:5


  9. The pH of human blood is approximately ______.
     Answer:35-7.45


  10. If a solution turns red litmus blue, it is ______ in nature.
     Answer: basic


 Chemical Reactions of Acids and Bases

  1. Acids react with metals to form ______ gas.
     Answer: hydrogen


  2. The reaction between an acid and a base is called a ______ reaction.
     Answer: neutralization


  3. The product formed in a neutralization reaction is ______ and ______.
     Answer: salt, water


  4. The reaction of an acid with a metal carbonate produces ______ gas.
     Answer: carbon dioxide


  5. The reaction of zinc with hydrochloric acid produces ______ gas.
     Answer: hydrogen


  6. The reaction of carbon dioxide with lime water forms ______, which makes the solution turn milky.
     Answer: calcium carbonate


  7. The chemical formula of lime water is ______.
     Answer: Ca(OH)₂


  8. The gas responsible for the “pop” sound when a burning matchstick is brought near is ______.
     Answer: hydrogen


  9. The reaction of baking soda with vinegar releases ______ gas.
     Answer: carbon dioxide


  10. The reaction of a base with a non-metallic oxide produces ______ and ______.
     Answer: salt, water


Common Salts and Their Uses

  1. The common name for sodium chloride is ______.
     Answer: table salt


  2. The chemical formula of baking soda is ______.
     Answer: NaHCO₃


  3. The chemical formula of washing soda is ______.
     Answer: Na₂CO₃.10H₂O


  4. The chemical formula of bleaching powder is ______.
     Answer: CaOCl₂


  5. The salt used in fire extinguishers is ______.
     Answer: sodium bicarbonate (NaHCO₃)


  6. ______ is the process used to manufacture sodium hydroxide from common salt.
     Answer: Chlor-alkali process


  7. Plaster of Paris is chemically known as ______.
     Answer: calcium sulfate hemihydrate (CaSO₄.½H₂O)


  8. Gypsum, when heated at 373K, forms ______.
     Answer: Plaster of Paris


  9. Washing soda is used for ______ water.
     Answer: softening


  10. The industrial preparation of sodium hydroxide involves the electrolysis of ______.
     Answer: brine (NaCl solution)


Water of Crystallization & Miscellaneous Questions

  1. Water of crystallization refers to the fixed number of ______ molecules in a salt.
     Answer: water


  2. The blue color of copper sulfate crystals is due to the presence of ______.
     Answer: water of crystallization


  3. When blue copper sulfate is heated, it turns ______.
     Answer: white


  4. The chemical formula of gypsum is ______.
     Answer: CaSO₄.2H₂O


  5. ______ is used for making decorative materials and medical bandages.
     Answer: Plaster of Paris


  6. The acid present in nettle stings is ______ acid.
     Answer: methanoic


  7. To treat an ant sting, apply a ______ solution.
     Answer: baking soda (NaHCO₃)


  8. The gas produced when an acid reacts with sodium bicarbonate is ______.
     Answer: carbon dioxide


  9. The pH of rainwater is usually slightly less than 7 due to the presence of dissolved ______.
     Answer: carbon dioxide


The phenomenon in which acids and bases cancel each other’s effects is called ______.
  Answer: neutralization

Name the Following

General Properties of Acids and Bases

  1. An acid that is found in lemon.
      Answer: Citric acid


  2. The base used in soap making.
      Answer: Sodium hydroxide (NaOH)


  3. A base that is soluble in water.
      Answer: Alkali


  4. The acid present in vinegar.
      Answer: Acetic acid


  5. A common base used in antacids.
      Answer: Magnesium hydroxide (Milk of Magnesia)


  6. The acid present in our stomach that helps in digestion.
      Answer: Hydrochloric acid (HCl)


  7. A base that is used in whitewashing.
      Answer: Calcium hydroxide (Slaked lime)


  8. A metallic oxide that reacts with acid to form salt and water.
      Answer: Basic oxide


  9. A non-metallic oxide that reacts with a base to form salt and water.
      Answer: Acidic oxide


  10. The substance responsible for the soapy feel of bases.
      Answer: Hydroxide ions (OH⁻)


Indicators and pH Scale

  1. A natural indicator obtained from lichen.
     Answer: Litmus


  2. The color of phenolphthalein in a basic solution.
     Answer: Pink


  3. The indicator that turns red in an acidic solution and yellow in a basic solution.
     Answer: Methyl orange


  4. The pH of a neutral solution.
     Answer: 7


  5. The range of the pH scale.
     Answer: 0 to 14


  6. The acid used in car batteries.
     Answer: Sulfuric acid (H₂SO₄)


  7. The gas released when an acid reacts with a metal.
     Answer: Hydrogen gas (H₂)


  8. The minimum pH value at which tooth enamel starts to decay.
     Answer:5


  9. The scale used to measure the strength of acids and bases.
     Answer: pH scale


  10. The acid present in curd.
     Answer: Lactic acid


 Chemical Reactions of Acids and Bases

  1. The reaction between an acid and a base to form salt and water.
     Answer: Neutralization reaction


  2. The gas released when acids react with metal carbonates or bicarbonates.
     Answer: Carbon dioxide (CO₂)


  3. The type of salt formed in a neutralization reaction.
     Answer: Neutral salt


  4. The compound formed when CO₂ is passed through lime water.
     Answer: Calcium carbonate (CaCO₃)


  5. The gas that turns lime water milky.
     Answer: Carbon dioxide (CO₂)


  6. The acid that is used in the preparation of soft drinks.
     Answer: Carbonic acid (H₂CO₃)


  7. A strong acid commonly used in laboratories.
     Answer: Hydrochloric acid (HCl)


  8. The base used in making window cleaners.
     Answer: Ammonium hydroxide (NH₄OH)


  9. The reaction in which an acid reacts with a metal to produce hydrogen gas.
     Answer: Acid-metal reaction


  10. The gas produced when zinc reacts with hydrochloric acid.
     Answer: Hydrogen gas (H₂)


Common Salts and Their Uses

  1. The common name of sodium chloride.
     Answer: Table salt


  2. The chemical name of baking soda.
     Answer: Sodium bicarbonate (NaHCO₃)


  3. The chemical name of washing soda.
     Answer: Sodium carbonate (Na₂CO₃.10H₂O)


  4. The chemical name of bleaching powder.
     Answer: Calcium oxychloride (CaOCl₂)


  5. A salt used in soda-acid fire extinguishers.
     Answer: Sodium bicarbonate (NaHCO₃)


  6. The salt used to remove permanent hardness of water.
     Answer: Washing soda (Na₂CO₃.10H₂O)


  7. The process used to manufacture sodium hydroxide from common salt.
     Answer: Chlor-alkali process


  8. A compound used in disinfecting drinking water.
     Answer: Bleaching powder (CaOCl₂)


  9. The salt used for making glass.
     Answer: Sodium carbonate (Na₂CO₃)


  10. The salt that decomposes to release carbon dioxide gas when heated.
     Answer: Sodium bicarbonate (NaHCO₃)


Water of Crystallization & Miscellaneous Questions

  1. The fixed number of water molecules present in a salt’s structure.
     Answer: Water of crystallization


  2. The blue salt that turns white on heating due to loss of water of crystallization.
     Answer: Copper sulfate pentahydrate (CuSO₄.5H₂O)


  3. The chemical formula of gypsum.
     Answer: CaSO₄.2H₂O


  4. The chemical name of Plaster of Paris.
     Answer: Calcium sulfate hemihydrate (CaSO₄.½H₂O)


  5. The salt used to make decorative materials and medical bandages.
     Answer: Plaster of Paris (POP)


  6. The acid present in ant stings.
     Answer: Methanoic acid (Formic acid)


  7. A mild base used to neutralize the effect of an ant sting.
     Answer: Baking soda (NaHCO₃)


  8. The gas evolved when an acid reacts with sodium bicarbonate.
     Answer: Carbon dioxide (CO₂)


  9. The acid responsible for acid rain. 
    Answer: Sulfuric acid (H₂SO₄)


  10. The process in which an acid and a base cancel each other’s effect.

  Answer: Neutralization

Answer in One Word

General Properties of Acids and Bases

  1. What is the taste of acids?
      Answer: Sour


  2. What is the taste of bases?
      Answer: Bitter


  3. Which ion is released by acids in aqueous solutions?
      Answer: H⁺ (Hydrogen ion)


  4. Which ion is released by bases in aqueous solutions?
      Answer: OH⁻ (Hydroxide ion)


  5. What is the pH of pure water?
      Answer: 7


  6. Which acid is found in vinegar?
      Answer: Acetic


  7. Which acid is found in lemon?
      Answer: Citric


  8. Which base is commonly used in soap making?
      Answer: Sodium hydroxide


  9. What is the other name for slaked lime?
      Answer: Calcium hydroxide


  10. What is the color of turmeric in a basic solution?
      Answer: Red


Indicators and pH Scale

  1. Which natural indicator is extracted from lichen?
     Answer: Litmus


  2. What is the color of phenolphthalein in an acidic solution?
     Answer: Colorless


  3. What is the color of phenolphthalein in a basic solution?
     Answer: Pink


  4. What is the pH range of acids?
     Answer: 0-6.9


  5. What is the pH range of bases?
     Answer:1-14


  6. Which indicator turns red in an acidic solution and yellow in a basic solution?
     Answer: Methyl orange


  7. What is the name of the scale used to measure acidity and alkalinity?
     Answer: pH scale


  8. What is the pH of gastric juice in the human stomach?
     Answer:5-3.5


  9. What is the minimum pH value at which tooth enamel starts to decay?
     Answer:5


  10. What is the chemical formula of lime water?
     Answer: Ca(OH)₂


 Chemical Reactions of Acids and Bases

  1. What gas is released when an acid reacts with a metal?
     Answer: Hydrogen


  2. What gas is released when an acid reacts with a carbonate?
     Answer: Carbon dioxide


  3. Which acid is found in ant stings?
     Answer: Methanoic


  4. What is the reaction between an acid and a base called?
     Answer: Neutralization


  5. What is the product of a neutralization reaction?
     Answer: Salt and water


  6. What is the chemical name of quick lime?
     Answer: Calcium oxide


  7. What is the chemical formula of hydrochloric acid?
     Answer: HCl


  8. What is the chemical formula of sulfuric acid?
     Answer: H₂SO₄


  9. What is the chemical formula of nitric acid?
     Answer: HNO₃


  10. What is the chemical formula of sodium hydroxide?
     Answer: NaOH


Common Salts and Their Uses

  1. What is the common name of sodium chloride?
     Answer: Table salt


  2. What is the chemical name of baking soda?
     Answer: Sodium bicarbonate


  3. What is the chemical name of washing soda?
     Answer: Sodium carbonate


  4. What is the chemical name of bleaching powder?
     Answer: Calcium oxychloride


  5. Which salt is used in soda-acid fire extinguishers?
     Answer: Sodium bicarbonate


  6. Which salt is used to remove permanent hardness of water?
     Answer: Washing soda


  7. What is the process used to manufacture sodium hydroxide from common salt?
     Answer: Chlor-alkali process


  8. Which compound is used to disinfect drinking water?
     Answer: Bleaching powder


  9. What is the common name of sodium carbonate?
     Answer: Washing soda


  10. What is the name of the salt that releases CO₂ gas when heated?
     Answer: Sodium bicarbonate


Water of Crystallization & Miscellaneous

  1. What is the fixed number of water molecules in a salt’s structure called?
     Answer: Water of crystallization


  2. What is the chemical formula of hydrated copper sulfate?
     Answer: CuSO₄.5H₂O


  3. What is the chemical formula of gypsum?
     Answer: CaSO₄.2H₂O


  4. What is the chemical name of Plaster of Paris?
     Answer: Calcium sulfate hemihydrate


  5. What is the common use of Plaster of Paris?
     Answer: Making casts


  6. Which acid is present in tamarind?
     Answer: Tartaric


  7. What should be applied to an ant sting to neutralize it?
     Answer: Baking soda


  8. What gas is evolved when an acid reacts with sodium bicarbonate?
     Answer: Carbon dioxide


  9. What is the acid responsible for acid rain? 

    Answer: Sulfuric acid


  10. What is the process in which an acid and a base cancel each other’s effect?

  Answer: Neutralization

CBSE - Grade 10 - Science

All Chapters

  • Science

    • Chapter 1 – Chemical Reactions and Equations
    • Chapter 2 – Acids, Bases and Salts
    • Chapter 3 – Metals and Non-metals
    • Chapter 4 – Carbon and its Compounds
    • Chapter 5 – Life Processes
    • Chapter 6 – Control and Coordination
    • Chapter 7 – How do Organisms Reproduce?
    • Chapter 8 – Heredity
    • Chapter 9 – Light – Reflection and Refraction
    • Chapter 10 – The Human Eye and the Colourful World
    • Chapter 11 – Electricity
    • Chapter 12 – Magnetic Effects of Electric Current
    • Chapter 13 – Our Environment

CBSE - Grade 10 - Mathematics

All Chapters

  • Ch 01 – Real Numbers
  • Ch 02 – Polynomials
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Find the Odd Man Out

General Properties of Acids and Bases

  1. Hydrochloric acid, Acetic acid, Sodium hydroxide, Sulfuric acid
      Odd one out: Sodium hydroxide (It is a base, others are acids)


  2. NaOH, KOH, Ca(OH)₂, H₂SO₄
      Odd one out: H₂SO₄ (It is an acid, others are bases)


  3. Blue litmus, Red litmus, Phenolphthalein, Lime water
      Odd one out: Lime water (It is a base, others are indicators)


  4. Bitter taste, Soapy touch, Turns blue litmus red, pH > 7
      Odd one out: Turns blue litmus red (It is a property of acids, others are properties of bases)


  5. Lemon juice, Vinegar, Baking soda, Tamarind
      Odd one out: Baking soda (It is a base, others are acids)


  6. HCl, NaCl, H₂SO₄, HNO₃
      Odd one out: NaCl (It is a salt, others are acids)


  7. Sodium hydroxide, Ammonium hydroxide, Potassium hydroxide, Acetic acid
      Odd one out: Acetic acid (It is an acid, others are bases)


  8. Water, NaOH, Ca(OH)₂, KOH
      Odd one out: Water (It is neutral, others are bases)


  9. Sodium hydroxide, Magnesium hydroxide, Ammonium hydroxide, Carbon dioxide
      Odd one out: Carbon dioxide (It is an acidic oxide, others are bases)


  10. Bitter taste, Slippery touch, Turns blue litmus red, pH > 7
      Odd one out: Turns blue litmus red (It is a property of acids, others are properties of bases)


Indicators and pH Scale

  1. pH 1, pH 3, pH 5, pH 10
     Odd one out: pH 10 (It is basic, others are acidic)


  2. pH 8, pH 9, pH 7, pH 12
     Odd one out: pH 7 (It is neutral, others are basic)


  3. Litmus, Phenolphthalein, Methyl orange, Sodium chloride
     Odd one out: Sodium chloride (It is a salt, others are indicators)


  4. Acid, Base, Neutralization, Oxidation
     Odd one out: Oxidation (It is not related to acid-base reactions)


  5. Methyl orange, Blue litmus, Red litmus, Ammonia
     Odd one out: Ammonia (It is a base, others are indicators)


  6. Blue litmus, Turmeric, Red litmus, Sodium chloride
     Odd one out: Sodium chloride (It is a salt, others are indicators)


  7. Colorless in acid, Pink in base, Turns red in acid, Turns green in base
     Odd one out: Turns green in base (This is not a property of common indicators)


  8. Acetic acid, Hydrochloric acid, Nitric acid, Ammonia
     Odd one out: Ammonia (It is a base, others are acids)


  9. pH paper, Phenolphthalein, Methyl orange, Baking soda
     Odd one out: Baking soda (It is a base, others are indicators)


  10. Lemon juice, Vinegar, Sodium bicarbonate, HCl
     Odd one out: Sodium bicarbonate (It is a base, others are acids)


 Chemical Reactions of Acids and Bases

  1. HCl + NaOH, H₂SO₄ + KOH, Na₂CO₃ + HCl, H₂ + O₂
     Odd one out: H₂ + O₂ (It is not an acid-base reaction)


  2. CaO, Na₂O, H₂O, K₂O
     Odd one out: H₂O (It is neutral, others are basic oxides)


  3. CO₂, SO₂, Na₂O, NO₂
     Odd one out: Na₂O (It is a basic oxide, others are acidic oxides)


  4. Zn + HCl, Fe + H₂SO₄, Cu + HNO₃, NaOH + HCl
     Odd one out: NaOH + HCl (It is a neutralization reaction, others involve metal-acid reaction)


  5. NaOH, HCl, CaCO₃, KOH
     Odd one out: CaCO₃ (It is a carbonate, others are acids or bases)


Common Salts and Their Uses

  1. NaCl, NaOH, KOH, Ca(OH)₂
     Odd one out: NaCl (It is a salt, others are bases)


  2. Bleaching powder, Baking soda, Washing soda, Hydrochloric acid
     Odd one out: Hydrochloric acid (It is an acid, others are salts)


  3. Table salt, Washing soda, Baking soda, Vinegar
     Odd one out: Vinegar (It is an acid, others are salts)


  4. NaCl, Na₂CO₃, NaHCO₃, H₂SO₄
     Odd one out: H₂SO₄ (It is an acid, others are salts)


  5. CaOCl₂, NaHCO₃, Na₂CO₃, NH₄OH
     Odd one out: NH₄OH (It is a base, others are salts)


Water of Crystallization & Miscellaneous

  1. CuSO₄.5H₂O, NaCl, FeSO₄.7H₂O, CaSO₄.2H₂O
     Odd one out: NaCl (It has no water of crystallization)


  2. Blue vitriol, Gypsum, Plaster of Paris, Baking soda
     Odd one out: Baking soda (It does not contain water of crystallization)


  3. Gypsum, Washing soda, Baking soda, Bleaching powder
     Odd one out: Bleaching powder (It does not contain water of crystallization)


  4. Water, Lemon juice, NaOH, H₂SO₄ 

    Odd one out: Water (It is neutral, others are acidic or basic)


  5. Soap, Detergent, Vinegar, NaOH

  Odd one out: Vinegar (It is acidic, others are basic)

Match the Pair

Set 1: General Properties of Acids and Bases

  1. Acids                        → (a) Bitter taste  
  2. Bases                        → (b) Sour taste  
  3. Turns blue litmus red        → (c) Basic in nature  
  4. Turns red litmus blue        → (d) Acidic in nature  
  5. Bases release                → (e) OH⁻ ions in water 

 

 Answers:
 1 → (b), 2 → (a), 3 → (d), 4 → (c), 5 → (e)

Set 2: Indicators and pH Scale

  1. pH of neutral solution       → (a) 4-6  
  2. pH of strong acid            → (b) 7  
  3. pH of weak acid              → (c) 11-14  
  4. pH of strong base            → (d) 0-3  
  5. Phenolphthalein in base      → (e) Pink 

 

 Answers:
 6 → (b), 7 → (d), 8 → (a), 9 → (c), 10 → (e)

Set 3: Chemical Reactions of Acids and Bases

  1. Acid + Metal                → (a) Salt + Water  
  2. Acid + Carbonate            → (b) NaCl + H₂O  
  3. Acid + Base                 → (c) Salt + CO₂ + H₂O  
  4. HCl + NaOH                  → (d) ZnSO₄ + H₂  
  5. NaOH + H₂SO₄                → (e) Na₂SO₄ + H₂O 

 

 Answers:
 11 → (d), 12 → (c), 13 → (a), 14 → (b), 15 → (e)

Set 4: Common Acids and Their Sources

  1. Citric acid                 → (a) Vinegar  
  2. Acetic acid                 → (b) Curd  
  3. Lactic acid                 → (c) Lemons  
  4. Tartaric acid               → (d) Ant stings  
  5. Methanoic acid              → (e) Tamarind 

 

 Answers:
 16 → (c), 17 → (a), 18 → (b), 19 → (e), 20 → (d)

Set 5: Common Salts and Their Uses

  1. Common salt                 → (a) Baking soda  
  2. Sodium bicarbonate          → (b) Bleaching powder  
  3. Sodium carbonate            → (c) Washing soda  
  4. Calcium oxychloride         → (d) NaCl  
  5. Used in detergents          → (e) Na₂CO₃.10H₂O 

 

 Answers:
 21 → (d), 22 → (a), 23 → (c), 24 → (b), 25 → (e)

Set 6: Water of Crystallization & Hydrated Salts

  1. Blue vitriol                → (a) CaSO₄.½H₂O  
  2. Gypsum                      → (b) CuSO₄.5H₂O  
  3. Plaster of Paris            → (c) CaSO₄.2H₂O  
  4. Water of Crystallization    → (d) Fixed water molecules in salts  
  5. Used in making casts        → (e) POP 

 

 Answers:
 26 → (b), 27 → (c), 28 → (a), 29 → (d), 30 → (e)

Set 7: Industrial Chemicals from Common Salt

  1. Used in soap making         → (a) NaHCO₃  
  2. Used in fire extinguishers  → (b) NaOH  
  3. Used to disinfect water     → (c) Na₂CO₃  
  4. Used to soften water        → (d) CaOCl₂  
  5. Used in baking industry     → (e) NaHCO₃ 

 

 Answers:
 31 → (b), 32 → (a), 33 → (d), 34 → (c), 35 → (e)

Set 8: Importance of pH in Daily Life

  1. Stomach acid                → (a) Tooth enamel decay  
  2. Acid rain                   → (b) Causes damage to buildings  
  3. Low pH in mouth             → (c) HCl  
  4. pH of pure water            → (d) 7  
  5. High pH in soil             → (e) Affects plant growth 

 

 Answers:
 36 → (c), 37 → (b), 38 → (a), 39 → (d), 40 → (e)

Set 9: Effects of Acids and Bases on Indicators

  1. Litmus in acid              → (a) Blue  
  2. Litmus in base              → (b) Red  
  3. Phenolphthalein in acid     → (c) Colorless  
  4. Phenolphthalein in base     → (d) Pink  
  5. Methyl orange in base       → (e) Yellow 

 

 Answers:
 41 → (b), 42 → (a), 43 → (c), 44 → (d), 45 → (e)

Set 10: Miscellaneous Questions

  1. Acid in car batteries       → (a) Citric acid  
  2. Gas evolved when acid reacts with metal → (b) CO₂  
  3. Used in whitewashing        → (c) Calcium hydroxide  
  4. pH of rainwater             → (d) Slightly acidic  
  5. Chemical used in antacids   → (e) Magnesium hydroxide 

 

 Answers:
 46 → (a), 47 → (b), 48 → (c), 49 → (d), 50 → (e)

Short Answer Questions  

General Properties of Acids and Bases

  1. What is the taste of acids and bases?  

    Answer: Acids are sour, and bases are bitter.  

 

  1. What happens when an acid is added to water?  

    Answer: It releases H⁺ ions, making the solution acidic.  

 

  1. What happens when a base is added to water?  

    Answer: It releases OH⁻ ions, making the solution basic.  

 

  1. How can you identify an acid using litmus paper?  

    Answer: Acids turn blue litmus red.  

 

  1. How can you identify a base using litmus paper?  

    Answer: Bases turn red litmus blue. 

 

Indicators and pH Scale

  1. What is the pH of pure water?  

    Answer: 7 (Neutral)  

 

  1. What is the pH range of acids?  

    Answer: Less than 7 (0-6.9)  

 

  1. What is the pH range of bases?  

    Answer: More than 7 (7.1-14)  

 

  1. What is the color of phenolphthalein in acids and bases?  

    Answer: Colorless in acids, pink in bases.  

 

  1. What is the color of methyl orange in acids and bases?  

     Answer: Red in acids, yellow in bases. 

 

 Chemical Reactions of Acids and Bases

  1. What happens when an acid reacts with a metal?  

     Answer: It forms salt and releases hydrogen gas.  

 

  1. Write the chemical equation for the reaction of zinc with hydrochloric acid.  

     Answer: Zn + 2HCl → ZnCl₂ + H₂↑  

 

  1. What happens when an acid reacts with a metal carbonate?  

     Answer: It forms salt, water, and carbon dioxide gas.  

 

  1. What is a neutralization reaction?  

     Answer: A reaction where an acid and a base react to form salt and water.  

 

  1. Give an example of a neutralization reaction.  

     Answer: NaOH + HCl → NaCl + H₂O 

 

Common Acids and Their Sources

  1. Name the acid present in vinegar.  

     Answer: Acetic acid  

 

  1. Name the acid present in lemons.  

     Answer: Citric acid  

 

  1. Which acid is present in curd?  

     Answer: Lactic acid  

 

  1. Which acid is found in ant stings?  

     Answer: Methanoic acid (Formic acid)  

 

  1. Which acid is used in car batteries?  

     Answer: Sulfuric acid (H₂SO₄) 

 

Common Salts and Their Uses

  1. What is the common name of sodium chloride (NaCl)?  

     Answer: Table salt  

 

  1. What is the chemical name of baking soda?  

     Answer: Sodium bicarbonate (NaHCO₃)  

 

  1. What is the chemical name of washing soda?  

     Answer: Sodium carbonate (Na₂CO₃.10H₂O)  

 

  1. What is the chemical name of bleaching powder?  

     Answer: Calcium oxychloride (CaOCl₂)  

 

  1. Which salt is used to remove hardness of water?  

     Answer: Washing soda (Na₂CO₃.10H₂O) 

 

 Water of Crystallization & Hydrated Salts

  1. What is water of crystallization?  

     Answer: Water molecules present in salt crystals.  

 

  1. What is the chemical formula of hydrated copper sulfate?  

     Answer: CuSO₄.5H₂O  

 

  1. What happens when hydrated copper sulfate is heated?  

     Answer: It turns white as it loses water of crystallization.  

 

  1. What is the chemical formula of gypsum?  

     Answer: CaSO₄.2H₂O  

 

  1. How is Plaster of Paris obtained from gypsum?  

     Answer: By heating gypsum at 373K. 

 

Importance of pH in Daily Life

  1. What is the pH of human blood?  

     Answer: Around 7.35-7.45  

 

  1. What is the pH of gastric juice?  

     Answer: Around 1.5-3.5  

 

  1. What happens when the pH of soil is too low?  

     Answer: It affects plant growth and may require lime treatment.  

 

  1. What happens when the pH of the mouth falls below 5.5?  

     Answer: Tooth enamel starts to decay.  

 

  1. What is the pH of acid rain?  

     Answer: Less than 5.6 

 

 Industrial Uses of Acids and Bases

  1. What is sodium hydroxide (NaOH) used for?  

     Answer: Making soaps, detergents, and paper.  

 

  1. What is sulfuric acid (H₂SO₄) used for?  

     Answer: Manufacturing fertilizers, car batteries, and detergents.  

 

  1. What is calcium hydroxide used for?  

     Answer: Used in whitewashing and neutralizing acidic soils.  

 

  1. What is the main chemical in fire extinguishers?  

     Answer: Sodium bicarbonate (NaHCO₃)  

 

  1. What is the purpose of bleaching powder?  

     Answer: Used to disinfect water and for bleaching fabrics. 

 

Effects of Acids and Bases on Indicators

  1. What is the color of litmus paper in acids?  

     Answer: Red  

 

  1. What is the color of litmus paper in bases?  

     Answer: Blue  

 

  1. What happens when turmeric is added to a base?  

     Answer: It turns red.  

 

  1. What is the color of methyl orange in acids?  

     Answer: Red  

 

  1. What is the color of methyl orange in bases?  

     Answer: Yellow 

 

Miscellaneous Questions

  1. What is the acid found in tomatoes?  

     Answer: Oxalic acid  

 

  1. What happens when an acid is mixed with water?  

     Answer: It dissociates to release H⁺ ions.  

 

  1. Why should acids be added to water and not vice versa?  

     Answer: To prevent splashing and heat generation.  

 

  1. Why is baking soda used in cooking?  

     Answer: It produces CO₂, making food fluffy.  

 

  1. What is the product formed when CO₂ is passed through lime water?  

     Answer: Calcium carbonate (CaCO₃), which makes lime water turn milky. 

Puzzles

Difference Between:

  1. Difference between Acids and Bases

Acids:

  • Acids are substances that release hydrogen ions (H⁺) in aqueous solutions.


  • They have a sour taste and turn blue litmus paper red.


  • Acids have a pH of less than 7.


  • Examples: Hydrochloric acid (HCl), Sulfuric acid (H₂SO₄).


Bases:

  • Bases are substances that release hydroxide ions (OH⁻) in aqueous solutions.


  • They have a bitter taste, feel slippery, and turn red litmus paper blue.


  • Bases have a pH greater than 7.


  • Examples: Sodium hydroxide (NaOH), Ammonium hydroxide (NH₄OH).


  1. Difference between Strong Acid and Weak Acid

Strong Acid:

  • Completely ionizes in water, producing a high concentration of H⁺ ions.


  • Has a lower pH (closer to 0).


  • Example: Hydrochloric acid (HCl), Nitric acid (HNO₃).


Weak Acid:

  • Partially ionizes in water, producing fewer H⁺ ions.


  • Has a pH closer to 7.


  • Example: Acetic acid (CH₃COOH), Citric acid.


  1. Difference between Strong Base and Weak Base

Strong Base:

  • Completely dissociates in water, releasing a high concentration of OH⁻ ions.


  • Has a higher pH (closer to 14).


  • Example: Sodium hydroxide (NaOH), Potassium hydroxide (KOH).


Weak Base:

  • Partially dissociates in water, releasing fewer OH⁻ ions.


  • Has a pH closer to 7.


  • Example: Ammonium hydroxide (NH₄OH).


  1. Difference between Organic Acid and Mineral Acid

Organic Acid:

  • Derived from living organisms and contains carbon.


  • Generally weak in nature.


  • Example: Acetic acid (vinegar), Citric acid (lemons).


Mineral Acid:

  • Derived from minerals and does not necessarily contain carbon.


  • Can be strong or weak acids.


  • Example: Hydrochloric acid (HCl), Sulfuric acid (H₂SO₄).


  1. Difference between Neutralization and Hydrolysis

Neutralization:

  • A reaction between an acid and a base to form salt and water.


  • pH moves toward neutral (7).


  • Example: HCl + NaOH → NaCl + H₂O.


Hydrolysis:

  • A reaction where a salt reacts with water to form an acidic or basic solution.


  • Example: NH₄Cl + H₂O → NH₄OH + HCl.


  1. Difference between Acidic Salt and Basic Salt

Acidic Salt:

  • Formed when a strong acid reacts with a weak base.


  • Produces an acidic solution in water.


  • Example: Ammonium chloride (NH₄Cl).


Basic Salt:

  • Formed when a strong base reacts with a weak acid.


  • Produces a basic solution in water.


  • Example: Sodium carbonate (Na₂CO₃).


  1. Difference between pH and pOH

pH:

  • Measures hydrogen ion (H⁺) concentration in a solution.


  • Formula: pH = -log[H⁺].


  • Indicates acidity or basicity of a solution.


pOH:

  • Measures hydroxide ion (OH⁻) concentration in a solution.


  • Formula: pOH = -log[OH⁻].


  • The sum of pH and pOH is always 14.


  1. Difference between Lime Water and Slaked Lime

Lime Water:

  • A clear solution of calcium hydroxide (Ca(OH)₂) in water.


  • Used to detect carbon dioxide (turns milky when CO₂ is passed through it).


Slaked Lime:

  • Solid calcium hydroxide (Ca(OH)₂).


  • Formed by adding water to quicklime (CaO).


  1. Difference between Washing Soda and Baking Soda

Washing Soda:

  • Chemically sodium carbonate (Na₂CO₃·10H₂O).


  • Used for cleaning and softening hard water.


Baking Soda:

  • Chemically sodium bicarbonate (NaHCO₃).


  • Used in baking, as an antacid, and in fire extinguishers.


  1. Difference between Bleaching Powder and Plaster of Paris

Bleaching Powder:

  • Chemically calcium oxychloride (CaOCl₂).


  • Used for disinfection and bleaching purposes.


Plaster of Paris:

  • Chemically calcium sulfate hemihydrate (CaSO₄·½H₂O).


Used in construction and medical applications (making casts).

Assertion and Reason

Instructions:

For each question, choose the correct option:
 (a) Both A and R are true, and R is the correct explanation of A.
 (b) Both A and R are true, but R is NOT the correct explanation of A.
 (c) A is true, but R is false.
 (d) A is false, but R is true.

 General Properties of Acids and Bases

  1. Assertion (A): Acids turn blue litmus red.
     Reason (R): Acids increase the concentration of H⁺ ions in solution.
      Answer: (a)


  2. Assertion (A): Bases have a soapy touch.
     Reason (R): Bases release OH⁻ ions in water.
      Answer: (a)


  3. Assertion (A): Acids taste sour, while bases taste bitter.
     Reason (R): Taste is determined by the pH of the solution.
      Answer: (b)


  4. Assertion (A): Sodium hydroxide is an acid.
     Reason (R): Sodium hydroxide releases H⁺ ions in water.
      Answer: (d)


  5. Assertion (A): Dry HCl gas does not change the color of dry litmus paper.
     Reason (R): HCl gas does not dissociate into H⁺ ions in the absence of water.
      Answer: (a)


Indicators and pH Scale

  1. Assertion (A): Phenolphthalein is pink in acids and colorless in bases.
    Reason (R): Phenolphthalein reacts with bases and forms a colored complex.
      Answer: (d)


  2. Assertion (A): pH value of a neutral solution is 7.
    Reason (R): A neutral solution has equal H⁺ and OH⁻ ion concentrations.
      Answer: (a)


  3. Assertion (A): The pH of pure water is always 7.
    Reason (R): Water undergoes self-ionization to form equal concentrations of H⁺ and OH⁻ ions.
      Answer: (b)


  4. Assertion (A): Lemon juice has a pH less than 7.
    Reason (R): Lemon juice contains citric acid.
      Answer: (a)


  5. Assertion (A): pH of 2 indicates a strong acid, while pH of 6 indicates a weak acid.
    Reason (R): The lower the pH, the stronger the acid.
      Answer: (a)


 Chemical Reactions of Acids and Bases

  1. Assertion (A): Acids react with metals to produce hydrogen gas.
    Reason (R): Metals displace hydrogen from acids due to their higher reactivity.
      Answer: (a)


  2. Assertion (A): When an acid reacts with a carbonate, CO₂ gas is released.
    Reason (R): Carbonates contain CO₃²⁻ ions, which react with H⁺ to form CO₂.
      Answer: (a)


  3. Assertion (A): Neutralization reactions always produce salt and water.
    Reason (R): Neutralization occurs when H⁺ and OH⁻ ions combine to form H₂O.
      Answer: (a)


  4. Assertion (A): A reaction between NaOH and HCl will result in the formation of NaCl and water.
    Reason (R): NaCl is formed when sodium and chlorine react in a neutralization reaction.
      Answer: (b)


  5. Assertion (A): Acetic acid is a strong acid.
    Reason (R): Acetic acid dissociates completely in water.
      Answer: (d)


Common Salts and Their Uses

  1. Assertion (A): Sodium chloride is a neutral salt.
    Reason (R): It is formed by the reaction of a strong acid (HCl) and a strong base (NaOH).
      Answer: (a)


  2. Assertion (A): Bleaching powder is used for water purification.
    Reason (R): Bleaching powder releases chlorine, which kills germs.
      Answer: (a)


  3. Assertion (A): Baking soda is acidic in nature.
    Reason (R): Baking soda is sodium bicarbonate (NaHCO₃), which is a weak base.
      Answer: (d)


  4. Assertion (A): Washing soda is used to remove hardness of water.
    Reason (R): Washing soda reacts with calcium and magnesium ions, forming insoluble compounds.
      Answer: (a)


  5. Assertion (A): Sodium bicarbonate is used in fire extinguishers.
    Reason (R): It decomposes to produce CO₂, which smothers the fire.
      Answer: (a)


Water of Crystallization & Miscellaneous

  1. Assertion (A): Water of crystallization is essential for the structure of some salts.
    Reason (R): The water molecules stabilize the crystal lattice of salts.
      Answer: (a)


  2. Assertion (A): Blue vitriol is the hydrated form of copper sulfate.
    Reason (R): Copper sulfate pentahydrate (CuSO₄.5H₂O) contains water of crystallization.
      Answer: (a)


  3. Assertion (A): Gypsum is used in making cement.
    Reason (R): Gypsum slows down the setting of cement.
      Answer: (a)


  4. Assertion (A): Plaster of Paris hardens when mixed with water. 

    Reason (R): Plaster of Paris absorbs water to form gypsum.
      Answer: (a)


  5. Assertion (A): Washing soda and baking soda have the same chemical formula.

 Reason (R): Both contain carbonate ions.
  Answer: (c)

True or False

  1. Acids taste sour and bases taste bitter. (True/False)  

    Answer: True  

 

  1. Bases turn blue litmus red. (True/False)  

    Answer: False  

 

  1. Acids release OH⁻ ions in water. (True/False)  

    Answer: False  

 

  1. The pH of pure water is 7. (True/False)  

    Answer: True  

 

  1. A solution with a pH of 10 is acidic. (True/False)  

    Answer: False 

 

Indicators and pH Scale

  1. Phenolphthalein is pink in acidic solutions. (True/False)  

    Answer: False  

 

  1. The pH of gastric juice is greater than 7. (True/False)  

    Answer: False  

 

  1. Acids turn red litmus blue. (True/False)  

    Answer: False  

 

  1. A neutral solution has an equal concentration of H⁺ and OH⁻ ions. (True/False)  

    Answer: True  

 

  1. A strong base has a pH less than 7. (True/False)  

     Answer: False 

 

 Chemical Reactions of Acids and Bases

  1. Acids react with metals to release hydrogen gas. (True/False)  

     Answer: True  

 

  1. Neutralization is a reaction between an acid and a base to form salt and oxygen. (True/False)  

     Answer: False  

 

  1. Carbonates react with acids to produce carbon dioxide gas. (True/False)  

     Answer: True  

 

  1. Zinc reacts with sulfuric acid to form zinc sulfate and hydrogen gas. (True/False)  

     Answer: True  

 

  1. A base reacts with a non-metal oxide to form a salt and water. (True/False)  

     Answer: True 

 

Common Salts and Their Uses

  1. Sodium chloride is commonly known as baking soda. (True/False)  

     Answer: False  

 

  1. Washing soda is used to remove hardness of water. (True/False)  

     Answer: True  

 

  1. Bleaching powder is used to disinfect drinking water. (True/False)  

     Answer: True  

 

  1. Sodium bicarbonate is used in baking and fire extinguishers. (True/False)  

     Answer: True  

 

  1. Sodium hydroxide is an acid. (True/False)  

     Answer: False 

 

Water of Crystallization & Hydrated Salts

  1. Gypsum is a hydrated salt. (True/False)  

     Answer: True  

 

  1. Plaster of Paris is obtained by heating gypsum. (True/False)  

     Answer: True  

 

  1. Copper sulfate without water of crystallization is blue in color. (True/False)  

     Answer: False  

 

  1. The chemical formula of Plaster of Paris is CaSO₄.2H₂O. (True/False)  

     Answer: False  

 

  1. Washing soda contains water of crystallization. (True/False)  

     Answer: True 

 

Importance of pH in Daily Life

  1. Tooth enamel starts to decay if the pH of the mouth falls below 5.5. (True/False)  

     Answer: True  

 

  1. A high pH level in soil makes it more acidic. (True/False)  

     Answer: False  

 

  1. Acid rain has a pH higher than 7. (True/False)  

     Answer: False  

 

  1. Blood has a pH of approximately 4.5. (True/False)  

     Answer: False  

 

  1. Vinegar has a pH less than 7. (True/False)  

     Answer: True 

 

Industrial Uses of Acids and Bases

  1. Sodium hydroxide is used in the manufacture of soap. (True/False)  

     Answer: True  

 

  1. Sulfuric acid is used in car batteries. (True/False)  

     Answer: True  

 

  1. Bleaching powder is used to soften hard water. (True/False)  

     Answer: False  

 

  1. Baking soda is used as an antacid. (True/False)  

     Answer: True  

 

  1. Calcium hydroxide is used in whitewashing. (True/False)  

     Answer: True 

 

Effects of Acids and Bases on Indicators

  1. Litmus paper turns blue in acid. (True/False)  

     Answer: False  

 

  1. Methyl orange turns yellow in acids. (True/False)  

     Answer: False  

 

  1. Phenolphthalein is colorless in neutral solutions. (True/False)  

     Answer: True  

 

  1. Turmeric turns red in a basic solution. (True/False)  

     Answer: True  

 

  1. Universal indicator shows different colors for different pH values. (True/False)  

     Answer: True 

 

Miscellaneous Questions

  1. Ammonia is a weak base. (True/False)  

     Answer: True  

 

  1. Hydrochloric acid is weaker than acetic acid. (True/False)  

     Answer: False  

 

  1. The reaction of a metal oxide with an acid produces salt and water. (True/False)  

     Answer: True  

 

  1. The reaction of sodium carbonate with hydrochloric acid produces hydrogen gas. (True/False)  

     Answer: False  

 

  1. Non-metal oxides are generally acidic in nature. (True/False)  

     Answer: True 

 

Additional Questions

  1. Toothpaste is acidic in nature. (True/False)  

     Answer: False  

 

  1. Acids can be stored in metal containers. (True/False)  

     Answer: False  

 

  1. Weak acids are completely ionized in water. (True/False)  

     Answer: False  

 

  1. The chemical formula of gypsum is CaSO₄.5H₂O. (True/False)  

     Answer: False  

 

  1. pH paper can be used to determine the pH of a solution. (True/False)  

     Answer: True 

Long Answer Questions

General Properties of Acids and Bases

  1. Explain the differences between acids and bases with examples.  

    Answer:  

   – Acids: Substances that release H⁺ ions in water, taste sour, and turn blue litmus red. Example: HCl, H₂SO₄.  

   – Bases: Substances that release OH⁻ ions in water, taste bitter, and turn red litmus blue. Example: NaOH, KOH.  

 

  1. How do acids and bases react with metals? Write chemical equations for both.  

    Answer:  

   – Acid + Metal → Salt + Hydrogen gas  

     Example: Zn + 2HCl → ZnCl₂ + H₂↑  

   – Base + Metal → Salt + Hydrogen gas (only with reactive metals like Zn, Al)  

     Example: 2NaOH + Zn → Na₂ZnO₂ + H₂↑  

 

  1. Describe the properties of acids and bases.  

    Answer:  

   – Acids: Sour taste, react with metals to produce H₂ gas, turn blue litmus red, conduct electricity.  

   – Bases: Bitter taste, soapy feel, react with acids to form salts, turn red litmus blue.  

 

  1. What are strong and weak acids? Give examples.  

    Answer:  

   – Strong Acids: Completely ionize in water (HCl, H₂SO₄).  

   – Weak Acids: Partially ionize in water (CH₃COOH, H₂CO₃).  

 

  1. What are strong and weak bases? Give examples.  

    Answer:  

   – Strong Bases: Completely ionize in water (NaOH, KOH).  

   – Weak Bases: Partially ionize in water (NH₄OH, Ca(OH)₂). 

 

Indicators and pH Scale

  1. What are indicators? Name three natural and three synthetic indicators.  

    Answer:  

   – Indicators: Substances that show different colors in acids and bases.  

   – Natural: Litmus, Turmeric, China Rose.  

   – Synthetic: Phenolphthalein, Methyl Orange, Universal Indicator.  

 

  1. Explain the pH scale with examples.  

    Answer:  

   – The pH scale (0-14) measures the acidity/basicity of a solution.  

   – Acids (pH < 7), Neutral (pH = 7), Bases (pH > 7).  

   – Example: Lemon juice (pH 2), Pure water (pH 7), Soap solution (pH 10).  

 

  1. Why is pH important in daily life? Explain with examples.  

    Answer:  

   – Digestion: Stomach acid (HCl) helps in digestion (pH ~1.5-3).  

   – Tooth Decay: Below pH 5.5, enamel dissolves.  

   – Soil pH: Affects plant growth (Neutral ~ 6-7).  

 

  1. How does pH affect the survival of aquatic life?  

    Answer:  

   – Acid rain (pH < 5.6) lowers the pH of water bodies.  

   – Affects fish and aquatic organisms that need a stable pH to survive.  

 

  1. How can farmers control soil pH for better crop growth?  

     Answer:  

    – If soil is too acidic → Add quicklime (CaO) or slaked lime (Ca(OH)₂).  

    – If soil is too basic → Add organic matter like compost or gypsum. 

 

 Chemical Reactions of Acids and Bases

  1. Explain neutralization reaction with examples.  

     Answer:  

    – Acid + Base → Salt + Water  

      Example: NaOH + HCl → NaCl + H₂O  

 

  1. How do acids react with metal carbonates and metal bicarbonates? Write balanced equations.  

     Answer:  

    – Acid + Metal Carbonate → Salt + Water + CO₂  

      Example: Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂  

    – Acid + Metal Bicarbonate → Salt + Water + CO₂  

      Example: NaHCO₃ + HCl → NaCl + H₂O + CO₂  

 

  1. Explain how acids and bases react with metal oxides.  

     Answer:  

    – Acid + Metal Oxide → Salt + Water  

      Example: CuO + H₂SO₄ → CuSO₄ + H₂O  

    – Base + Non-Metal Oxide → Salt + Water  

      Example: CO₂ + Ca(OH)₂ → CaCO₃ + H₂O  

 

  1. What happens when acid rain affects buildings and monuments?  

     Answer:  

    – Acid rain (H₂SO₄, HNO₃) reacts with limestone (CaCO₃), causing erosion.  

      Example: CaCO₃ + H₂SO₄ → CaSO₄ + H₂O + CO₂  

 

  1. What happens when ammonia reacts with an acid? Write the chemical equation.  

     Answer:  

    – NH₃ + HCl → NH₄Cl (Forms Ammonium chloride) 

 

Common Salts and Their Uses

  1. How is common salt (NaCl) obtained?  

     Answer:  

    – From seawater through evaporation.  

 

  1. How is sodium hydroxide (NaOH) prepared? Write the reaction.  

     Answer:  

    – Through the Chlor-alkali process.  

      2NaCl + 2H₂O → 2NaOH + Cl₂ + H₂ (Electrolysis of brine).  

 

  1. Write the chemical formula and uses of:  

     Answer:  

    – Baking soda: NaHCO₃ (Antacid, Fire extinguisher).  

    – Washing soda: Na₂CO₃.10H₂O (Softens water, Detergent).  

    – Bleaching powder: CaOCl₂ (Disinfectant, Textile bleaching).  

 

  1. How is Plaster of Paris (POP) prepared? Write the reaction.  

     Answer:  

    – By heating gypsum at 373K.  

      CaSO₄.2H₂O → CaSO₄.½H₂O + 1.5H₂O  

 

  1. Why should POP be stored in moisture-proof containers?  

     Answer:  

    – It reacts with moisture and hardens into gypsum. 

 

Miscellaneous Questions

  1. Why should acids be added to water and not vice versa?  

     Answer:  

    – Adding water to acid causes splashing and heat release, which is dangerous.  

 

  1. Why do pickles and curd spoil in metal containers?  

     Answer:  

    – Acids in pickles and curd react with metals to form harmful salts.  

 

  1. How does baking soda help in cooking?  

     Answer:  

    – It releases CO₂ gas, making the food fluffy.  

 

  1. Why is toothpaste basic in nature?  

     Answer:  

    – To neutralize acids in the mouth and prevent tooth decay.  

 

  1. What is the role of acids and bases in industries?  

     Answer:  

    – Acids: Used in fertilizers, batteries, food processing.  

    – Bases: Used in soaps, detergents, textiles. 

 

 Advanced Concepts of Acids, Bases, and Salts

  1. How does acid rain occur? What are its effects on the environment?  

     Answer:  

    – Acid rain occurs when sulfur dioxide (SO₂) and nitrogen oxides (NO₂) react with water in the atmosphere to form sulfuric acid (H₂SO₄) and nitric acid (HNO₃).  

    – Effects:  

      – Lowers soil pH, affecting plant growth.  

      – Harms aquatic life by making water bodies acidic.  

      – Damages buildings and monuments made of limestone.  

 

  1. Why does an aqueous solution of an acid conduct electricity?  

     Answer:  

    – Acids ionize in water to form H⁺ (hydrogen ions), which are responsible for conducting electricity.  

    – Example: HCl → H⁺ + Cl⁻ (Free-moving ions allow electric current to pass).  

 

  1. Why does dry HCl gas not change the color of dry litmus paper, but moist HCl does?  

     Answer:  

    – Dry HCl gas does not release H⁺ ions without water.  

    – In the presence of water, HCl ionizes and releases H⁺, which changes the litmus color.  

 

  1. How do concentrated acids and dilute acids differ in terms of strength and conductivity?  

     Answer:  

    – **Strength**: Concentrated acids have more H⁺ ions per unit volume, making them stronger.  

    – **Conductivity**: Higher ion concentration in concentrated acids increases conductivity.  

 

  1. Why is rainwater slightly acidic? What happens when CO₂ dissolves in water?  

     Answer:  

    – CO₂ dissolves in rainwater forming carbonic acid (H₂CO₃), making rainwater naturally acidic.  

    – CO₂ + H₂O → H₂CO₃ (Weak acid). 

 

pH and Its Applications

  1. Why is pH important in medicine? Give two examples.  

     Answer:  

    – **Blood pH**: Must be around 7.35-7.45 for proper functioning.  

    – **Digestive system**: Medicines like antacids neutralize stomach acid (pH 1.5-3.5).  

 

  1. How does pH play a role in food preservation?  

     Answer:  

    – Acids like vinegar (acetic acid) prevent bacterial growth.  

    – Lemon juice (citric acid) preserves jams and pickles.  

 

  1. Why does the pH of milk change when it turns sour?  

     Answer:  

    – Lactic acid forms when bacteria ferment lactose, lowering pH.  

    – Fresh milk (pH ~6.5), sour milk (pH ~4-5).  

 

  1. How do pH changes affect aquatic life?  

     Answer:  

    – pH below 5.5 in water bodies harms fish and aquatic plants.  

    – Neutral pH (6.5-7.5) is ideal for aquatic organisms.  

 

  1. What is the role of pH in maintaining soil fertility?  

     Answer:  

    – Soil pH affects nutrient availability.  

    – Acidic soil (pH < 6) is treated with lime (CaO).  

    – Alkaline soil (pH > 7.5) is treated with gypsum (CaSO₄). 

 

 Reactions of Acids, Bases, and Salts

  1. Why should acid containers be made of glass and not metal?  

     Answer:  

    – Acids react with metals to produce hydrogen gas, leading to corrosion.  

    – Glass is unreactive, making it a safer storage material.  

 

  1. Why do we store pickles and curd in glass or plastic containers?  

     Answer:  

    – Pickles and curd contain acids that react with metal containers, forming harmful salts.  

 

  1. Explain why ammonium hydroxide (NH₄OH) is a weak base.  

     Answer:  

    – NH₄OH only partially ionizes in water, releasing fewer OH⁻ ions.  

 

  1. Why is slaked lime used to neutralize acidic industrial waste?  

     Answer:  

    – Slaked lime (Ca(OH)₂) reacts with acids to form neutral salts, preventing environmental damage.  

 

  1. Why do bee stings cause pain, and how can it be relieved?  

     Answer:  

    – Bee venom contains formic acid, which causes pain and swelling.  

    – Applying baking soda (NaHCO₃) neutralizes the acid. 

 

Industrial and Household Applications

  1. How is sodium hydroxide (NaOH) prepared in industries? Write the reaction.  

     Answer:  

    – Prepared by electrolysis of brine in the **Chlor-alkali process**.  

    – Reaction: 2NaCl + 2H₂O → 2NaOH + Cl₂ + H₂.  

 

  1. How is washing soda (Na₂CO₃.10H₂O) prepared?  

     Answer:  

    – Made by heating baking soda (NaHCO₃) to form sodium carbonate, which is then crystallized with water.  

    – NaHCO₃ → Na₂CO₃ → Na₂CO₃.10H₂O.  

 

  1. How does bleaching powder help in water purification?  

     Answer:  

    – Releases chlorine, which kills harmful bacteria and germs.  

    – CaOCl₂ + H₂O → Ca(OH)₂ + Cl₂.  

 

  1. How does baking soda help in fire extinguishers?  

     Answer:  

    – Decomposes to release CO₂, which displaces oxygen and smothers flames.  

    – 2NaHCO₃ → Na₂CO₃ + CO₂ + H₂O.  

 

  1. How is Plaster of Paris (POP) used in the medical field?  

     Answer:  

    – Used to make orthopedic casts for broken bones.  

    – Hardens when mixed with water, forming gypsum. 

 

Miscellaneous Questions

  1. Why does an iron nail corrode faster in acid than in water?  

     Answer:  

    – Acids react with iron to form soluble salts, speeding up rusting.  

 

  1. How does ammonia neutralize acids in fertilizers?  

     Answer:  

    – Ammonia (NH₃) reacts with acids to form ammonium salts, improving soil fertility.  

 

  1. What happens when excess carbon dioxide is passed through lime water?  

     Answer:  

    – Initially, lime water turns milky due to CaCO₃ formation.  

    – Excess CO₂ dissolves CaCO₃, clearing the solution.  

 

  1. How does the pH of shampoo differ from that of soap?  

     Answer:  

    – Shampoo (pH ~5-6) is mildly acidic to prevent hair damage.  

    – Soap (pH ~9-10) is basic to remove grease.  

 

  1. Why does antacid relieve acidity?  

     Answer:  

    – Antacids (like Mg(OH)₂) neutralize excess stomach acid, reducing heartburn. 

Give Reasons

General Properties of Acids and Bases

  1. Give reason: Acids have a sour taste.  

    Answer: Acids release H⁺ ions in aqueous solutions, which stimulate the sour taste receptors on the tongue.  

 

  1. Give reason: Bases have a bitter taste and a slippery feel.  

    Answer: Bases release OH⁻ ions in water, which give them a soapy texture and bitter taste.  

 

  1. Give reason: Acids turn blue litmus red.  

    Answer: Acids increase the concentration of H⁺ ions, which react with blue litmus, turning it red.  

 

  1. Give reason: Bases turn red litmus blue.  

    Answer: Bases release OH⁻ ions, which neutralize the acidic property of red litmus, turning it blue.  

 

  1. Give reason: Sodium hydroxide (NaOH) is a strong base.  

    Answer: It completely ionizes in water to release OH⁻ ions, making the solution highly basic. 

 

Indicators and pH Scale

  1. Give reason: The pH of pure water is 7.  

    Answer: Pure water has an equal concentration of H⁺ and OH⁻ ions, making it neutral.  

 

  1. Give reason: The pH of stomach acid is low.  

    Answer: Stomach acid contains HCl, which aids digestion by breaking down food and killing harmful bacteria.  

 

  1. Give reason: A solution with a pH of 2 is more acidic than one with a pH of 5.  

    Answer: The pH scale is logarithmic, meaning a decrease of one unit increases acidity 10 times.  

 

  1. Give reason: Acids should be handled carefully.  

    Answer: Strong acids like H₂SO₄ and HCl can cause burns and react violently with water and metals.  

 

  1. Give reason: The pH of rainwater is slightly less than 7.  

     Answer: Rainwater dissolves CO₂ from the atmosphere, forming weak carbonic acid (H₂CO₃). 

 

 Chemical Reactions of Acids and Bases

  1. Give reason: Acids react with metals to produce hydrogen gas.  

     Answer: Metals replace hydrogen in acids, forming salt and releasing H₂ gas.  

    Example: Zn + 2HCl → ZnCl₂ + H₂↑  

 

  1. Give reason: Carbon dioxide is released when acids react with carbonates.  

     Answer: Carbonates contain CO₃²⁻ ions, which react with H⁺ ions from acids to form CO₂ gas.  

 

  1. Give reason: Neutralization reactions are useful in agriculture.  

     Answer: Acidic or basic soils can be neutralized using bases (lime) or acids (gypsum) to improve fertility.  

 

  1. Give reason: Brushing teeth with toothpaste prevents cavities.  

     Answer: Toothpaste is basic and neutralizes acids formed by bacteria in the mouth, preventing enamel damage.  

 

  1. Give reason: Antacids are used to treat acidity.  

     Answer: Antacids like Mg(OH)₂ neutralize excess stomach acid (HCl) and relieve heartburn. 

 

Common Salts and Their Uses

  1. Give reason: Baking soda is used in cooking.  

     Answer: Baking soda (NaHCO₃) releases CO₂ gas when heated, making food soft and fluffy.  

 

  1. Give reason: Washing soda is used for cleaning.  

     Answer: Washing soda (Na₂CO₃.10H₂O) softens hard water by removing Ca²⁺ and Mg²⁺ ions.  

 

  1. Give reason: Bleaching powder is used in water treatment.  

     Answer: Bleaching powder (CaOCl₂) releases chlorine, which kills harmful microorganisms in water.  

 

  1. Give reason: Plaster of Paris is stored in moisture-proof containers.  

     Answer: POP absorbs moisture and converts into hard gypsum, making it unusable.  

 

  1. Give reason: Common salt (NaCl) is used as a preservative.  

     Answer: It prevents bacterial growth by drawing water out of microbial cells through osmosis. 

 

Water of Crystallization & Hydrated Salts

  1. Give reason: Blue vitriol turns white on heating.  

     Answer: Blue vitriol (CuSO₄.5H₂O) loses water of crystallization upon heating, turning white.  

 

  1. Give reason: Plaster of Paris hardens when mixed with water.  

     Answer: It reacts with water to form gypsum, which solidifies quickly.  

 

  1. Give reason: Some salts appear dry but contain water molecules.  

     Answer: These salts have water of crystallization trapped within their crystal structure.  

 

  1. Give reason: Gypsum is used in cement making.  

     Answer: It slows down the setting process of cement, allowing time for construction.  

 

  1. Give reason: Washing soda is crystalline but not dry.  

     Answer: It contains 10 water molecules as water of crystallization (Na₂CO₃.10H₂O). 

 

 Importance of pH in Daily Life

  1. Give reason: Bee stings are treated with baking soda.  

     Answer: Bee venom contains formic acid, which is neutralized by baking soda (a base).  

 

  1. Give reason: Soil pH affects plant growth.  

     Answer: Different plants require different pH levels for optimal nutrient absorption.  

 

  1. Give reason: Fish cannot survive in acidic lakes.  

     Answer: Acidic water affects oxygen availability and disrupts aquatic ecosystems.  

 

  1. Give reason: Farmers add lime to acidic soil.  

     Answer: Lime (CaO) neutralizes excess acidity, improving soil fertility.  

 

  1. Give reason: Rainwater is more acidic in industrial areas.  

     Answer: Factories release SO₂ and NO₂, which dissolve in rainwater to form acid rain. 

 

Industrial and Household Applications

  1. Give reason: Hydrochloric acid is used in cleaning toilets.  

     Answer: It dissolves stains and mineral deposits.  

 

  1. Give reason: Sodium hydroxide is used in soap making.  

     Answer: It reacts with fats and oils to form soap (saponification).  

 

  1. Give reason: Acidic foods should not be stored in metal containers.  

     Answer: Acids react with metals to form toxic salts.  

 

  1. Give reason: Fire extinguishers contain sodium bicarbonate.  

     Answer: It releases CO₂, which displaces oxygen and smothers fire.  

 

  1. Give reason: Detergents work better than soaps in hard water.  

     Answer: Soaps form scum with hard water, but detergents do not. 

 

Miscellaneous Questions

  1. Give reason: Toothpaste is basic.  

     Answer: It neutralizes acids that cause tooth decay.  

 

  1. Give reason: Alkalis are used in window cleaners.  

     Answer: They dissolve grease and dirt effectively.  

 

  1. Give reason: Vinegar is used to remove rust from metals.  

     Answer: Acetic acid reacts with iron oxide, dissolving rust.  

 

  1. Give reason: Ant bites cause irritation.  

     Answer: Ant venom contains formic acid, which irritates the skin.  

 

  1. Give reason: Sugar does not change the color of litmus paper.  

     Answer: Sugar is a neutral compound with no acidic or basic properties. 

Arrange the Words 

Case Studies

Numericals

Basic pH Calculations

  1. Calculate the pH of a solution with [H⁺] = 1 × 10⁻³ M.  

    Answer: pH = -log(1 × 10⁻³) = 3  

 

  1. Find the pH of a solution where [OH⁻] = 1 × 10⁻⁶ M.  

    Answer: pOH = -log(1 × 10⁻⁶) = 6, pH = 14 – 6 = 8  

 

  1. If a solution has a pH of 5, what is the concentration of H⁺ ions?  

    Answer: [H⁺] = 10⁻⁵ M  

 

  1. A solution has a pOH of 4. Find its pH.  

    Answer: pH = 14 – pOH = 14 – 4 = 10  

 

  1. The hydrogen ion concentration of a solution is 1 × 10⁻⁹ M. What is its pH?  

    Answer: pH = -log(1 × 10⁻⁹) = 9 

 

Neutralization Reactions

  1. How many moles of NaOH are required to neutralize 2 moles of HCl?  

    Answer: 2 moles (since NaOH + HCl → NaCl + H₂O, 1:1 ratio)  

 

  1. 50 mL of 0.1 M HCl is neutralized by NaOH. Find the volume of 0.1 M NaOH required.  

    Answer: (M₁V₁ = M₂V₂)  

             (0.1 × 50) = (0.1 × V₂)  

             V₂ = 50 mL  

 

  1. How much 0.5 M H₂SO₄ is needed to neutralize 100 mL of 1 M NaOH?  

    Answer: (n₁M₁V₁ = n₂M₂V₂)  

             (2 × 0.5 × V₁) = (1 × 1 × 100)  

             V₁ = 100 mL  

 

  1. A student adds 0.5 moles of NaOH to 250 mL of 1 M HCl. Determine if the solution is neutral, acidic, or basic.  

    Answer:  

   – Moles of HCl = 1 × 0.25 = 0.25 moles  

   – Moles of NaOH = 0.5 moles  

   – Excess NaOH = 0.5 – 0.25 = 0.25 moles (Basic solution)  

 

  1. How many grams of NaOH are required to neutralize 0.2 moles of H₂SO₄?  

     Answer: 0.4 moles (since 2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O)  

              Mass = 0.4 × 40 = 16 g 

 

 Molarity and Dilution

  1. Calculate the molarity of 2 moles of HCl in 500 mL of solution.  

     Answer: M = n/V = 2/0.5 = 4 M  

 

  1. What is the molarity of a solution prepared by dissolving 10 g of NaOH in 250 mL of water?  

     Answer: M = (mass / molar mass) / volume  

              M = (10 / 40) / 0.25  

              M = 1 M  

 

  1. How much water must be added to 100 mL of 1 M HCl to dilute it to 0.2 M?  

     Answer: M₁V₁ = M₂V₂  

              (1 × 100) = (0.2 × V₂)  

              V₂ = 500 mL  

              Water added = 500 – 100 = 400 mL  

 

  1. Find the volume of 2 M HCl needed to prepare 250 mL of 0.5 M HCl.  

     Answer: M₁V₁ = M₂V₂  

              (2 × V₁) = (0.5 × 250)  

              V₁ = 62.5 mL  

 

  1. What is the molarity of a solution containing 49 g of H₂SO₄ in 1 L of solution? (Molar mass of H₂SO₄ = 98 g/mol)  

     Answer: M = 49/98 = 0.5 M 

 

Stoichiometry-Based Problems

  1. How many moles of CO₂ are produced when 1 mole of Na₂CO₃ reacts with HCl?  

     Answer: 1 mole (Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂)  

 

  1. Calculate the mass of NaCl formed when 50 g of NaOH reacts with HCl.  

     Answer: Moles of NaOH = 50/40 = 1.25  

              Mass of NaCl = 1.25 × 58.5 = 73.1 g  

 

  1. How many grams of Na₂CO₃ are required to neutralize 100 mL of 1 M HCl?  

     Answer: Moles of HCl = 1 × 0.1 = 0.1  

              Moles of Na₂CO₃ = 0.05 (1:2 ratio)  

              Mass = 0.05 × 106 = 5.3 g  

 

  1. Calculate the volume of CO₂ produced at STP when 0.5 moles of CaCO₃ reacts with HCl.  

     Answer: 0.5 moles of CO₂  

              Volume at STP = 0.5 × 22.4 = 11.2 L  

 

  1. Determine the mass of CaSO₄ formed when 2 moles of H₂SO₄ react with Ca(OH)₂.  

     Answer: 2 moles of H₂SO₄ give 2 moles of CaSO₄  

              Mass = 2 × 136 = 272 g 

 

Real-Life Applications

  1. How much NaHCO₃ is required to neutralize 100 mL of vinegar (1 M CH₃COOH)?  

     Answer: Moles of CH₃COOH = 1 × 0.1 = 0.1  

              Moles of NaHCO₃ = 0.1  

              Mass = 0.1 × 84 = 8.4 g  

 

  1. If 2 g of NaOH is dissolved in 250 mL of water, find the normality of the solution.  

     Answer: Normality (N) = (Mass × 1) / (Eq. wt × Volume in L)  

              Eq. wt of NaOH = 40  

              N = (2 × 1) / (40 × 0.25) = 0.2 N  

 

  1. How much Ca(OH)₂ is required to neutralize 50 mL of 1 M HCl?  

     Answer: Moles of HCl = 1 × 0.05 = 0.05  

              Moles of Ca(OH)₂ = 0.025 (1:2 ratio)  

              Mass = 0.025 × 74 = 1.85 g  

 

  1. Find the amount of HCl needed to dissolve 10 g of CaCO₃.  

     Answer: Moles of CaCO₃ = 10/100 = 0.1  

              Moles of HCl required = 0.2 (1:2 ratio)  

              Mass = 0.2 × 36.5 = 7.3 g  

 

  1. A buffer solution has a pH of 4.5. If [H⁺] is increased, what happens to the pH?  

     Answer: The pH decreases. 

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