Answers provided with explanation.
Q1–Q10
- Which of the following is a natural indicator?
a) Phenolphthalein
b) Methyl orange
c) Litmus
d) Turmeric - Which of these is an example of a strong acid?
a) Acetic acid
b) Hydrochloric acid
c) Citric acid
d) Lactic acid - Which gas is released when an acid reacts with a metal carbonate?
a) CO₂
b) SO₂
c) H₂
d) O₂ - Which ion is responsible for the acidic nature of a solution?
a) OH⁻
b) H⁺ (or H₃O⁺)
c) Na⁺
d) Cl⁻ - Which type of salt is CH₃COONa?
a) Neutral
b) Acidic
c) Basic
d) Amphoteric - Which compound is used to manufacture bleaching powder?
a) NaCl
b) Ca(OH)₂
c) CaCO₃
d) CaSO₄ - Plaster of Paris is chemically:
a) CaSO₄·2H₂O
b) CaSO₄·½H₂O
c) Ca(OH)₂
d) CaCO₃ - pH of a basic solution is:
a) 7
b) Less than 7
c) More than 7
d) Exactly 0 - Which acid is present in ant sting?
a) Formic acid
b) Acetic acid
c) Oxalic acid
d) Citric acid - The chemical name of baking soda is:
a) Sodium carbonate
b) Sodium bicarbonate
c) Sodium hydroxide
d) Calcium carbonate
Q11–Q20
- Which of these shows acidic behaviour in water?
a) NaCl
b) Na₂CO₃
c) HCl
d) KOH - Which property is true for bases?
a) Turn blue litmus red
b) Turn red litmus blue
c) Release H⁺ ions
d) Taste sour - Which gas is released when Zn reacts with dilute H₂SO₄?
a) CO₂
b) H₂
c) SO₂
d) O₂ - Which salt is obtained from a strong acid and a strong base?
a) NaCl
b) CH₃COONa
c) NH₄Cl
d) Na₂CO₃ - The pH of milk of magnesia is:
a) 7
b) Less than 7
c) More than 7
d) 0 - Which acid is used in the manufacture of fertilizers?
a) Nitric acid
b) Acetic acid
c) Tartaric acid
d) Oxalic acid - The process of dissolving an acid or base in water is:
a) Neutralization
b) Dilution
c) Saturation
d) Oxidation - Which of the following is an amphoteric oxide?
a) CO₂
b) ZnO
c) MgO
d) SO₂ - Which of these will have a pH close to 14?
a) NaOH solution
b) HCl solution
c) Milk
d) Lemon juice - Washing soda is chemically:
a) Na₂CO₃·10H₂O
b) NaHCO₃
c) NaCl
d) K₂CO₃
Q21–Q30
- What will be the pH of a neutral solution at 25°C?
a) 0
b) 7
c) 14
d) Cannot be predicted - Tooth decay starts when pH of mouth:
a) Falls below 7
b) Falls below 5.5
c) Rises above 7
d) Rises above 9 - Which gas turns lime water milky?
a) CO₂
b) SO₂
c) NH₃
d) O₂ - Slaked lime is chemically:
a) Ca(OH)₂
b) CaO
c) CaCO₃
d) CaSO₄ - Which of these is a weak base?
a) NaOH
b) KOH
c) NH₄OH
d) Ca(OH)₂ - Which acid is present in vinegar?
a) Formic acid
b) Acetic acid
c) Oxalic acid
d) Citric acid - Which is used in antacid tablets?
a) NaOH
b) Mg(OH)₂
c) H₂SO₄
d) KOH - Which of these salts is used in cold packs?
a) NaCl
b) NH₄NO₃
c) CaSO₄
d) K₂SO₄ - The pH paper turns red for:
a) Acidic solution
b) Basic solution
c) Neutral solution
d) Salt solution only - Which base is soluble in water?
a) NaOH
b) Fe(OH)₃
c) Cu(OH)₂
d) Al(OH)₃
Answers with Explanations
Q1–Q10
- c) Litmus – Natural dye from lichens; turns red in acids, blue in bases. Turmeric is also natural but mainly detects bases.
- b) Hydrochloric acid – Strong acid, completely ionizes in water.
- a) CO₂ – Acid + metal carbonate → salt + water + carbon dioxide.
- b) H⁺ (or H₃O⁺) – Acidity is due to hydrogen ions in aqueous solution.
- c) Basic – Sodium acetate (CH₃COONa) comes from strong base + weak acid → basic salt.
- b) Ca(OH)₂ – Bleaching powder is made by passing Cl₂ gas over dry slaked lime.
- b) CaSO₄·½H₂O – Formula of Plaster of Paris.
- c) More than 7 – Basic solutions have pH > 7.
- a) Formic acid – Present in ant stings; formula HCOOH.
- b) Sodium bicarbonate – Baking soda; formula NaHCO₃.
Q11–Q20
- c) HCl – Releases H⁺ ions in water → acidic behaviour.
- b) Turn red litmus blue – Bases change red litmus to blue.
- b) H₂ – Metal + acid → salt + hydrogen gas.
- a) NaCl – Neutral salt formed from strong acid + strong base.
- c) More than 7 – Milk of magnesia is a suspension of Mg(OH)₂ (basic).
- a) Nitric acid – Used in fertilizers like ammonium nitrate.
- b) Dilution – Adding acid/base to water lowers concentration.
- b) ZnO – Amphoteric oxide; reacts with both acids and bases.
- a) NaOH solution – Strong base, pH close to 14.
- a) Na₂CO₃·10H₂O – Washing soda formula.
Q21–Q30
- b) 7 – Neutral solution has equal H⁺ and OH⁻ concentrations.
- b) Falls below 5.5 – Below this pH, enamel starts dissolving.
- a) CO₂ – Forms insoluble CaCO₃ with limewater → milky appearance.
- a) Ca(OH)₂ – Slaked lime formula.
- c) NH₄OH – Weak base; partially ionizes in water.
- b) Acetic acid – Main acid in vinegar; CH₃COOH.
- b) Mg(OH)₂ – Used in antacids to neutralize stomach acid.
- b) NH₄NO₃ – Dissolves endothermically → used in cold packs.
- a) Acidic solution – Red colour in pH paper means acidic.
- a) NaOH – Strong alkali, soluble in water (alkali = soluble base).