All 24 MCQs of 9th Class Chemistry Chapter 7, Acid Base Chemistry, with answers and the reason each option is right or wrong: the 10 textbook exercise MCQs plus 14 more board-style MCQs. Punjab Board new syllabus.
Try each one first: tap an option to check it, then read the reasoning and why the others are wrong.
A note about the questions
The wording follows published solved exercises and every answer was re-checked by hand, so the wording or the order of options may differ slightly from your print.
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Set A: Textbook exercise 10 MCQs
The multiple-choice questions at the end of Chapter 7 in your book, in the book's option order.
Q7.1Acids, Bases and Alkalis
Which acid is not used as a food or mixed with food?
Answer(d) Formic acid
Step by step
Table 7.1: formic acid comes from ant sting.
The other three come from fruits.
Why the others are wrong
(a) tartaric acid is in tamarind (imli).
(b) ascorbic acid is vitamin C.
(c) citric acid is in lemons and is added to drinks.
Remember
Ant sting is not food.
Q7.2Reactions of Acids and Bases
While baking, which gas is responsible for raising the bread and making it soft?
Answer(b) Carbon dioxide
Step by step
NaHCO₃ + acid → salt + H₂O + CO₂.
Gas bubbles expand in the oven.
Why the others are wrong
(a) oxygen is not produced.
(c) nitrogen takes no part.
(d) CO is poisonous and is not formed.
Remember
Bubbles in bread = CO₂.
Q7.3Reactions of Acids and Bases
Predict the main characteristics of the reactions of metals with acids.
Answer(d) All the above mentioned characteristics are true
Step by step
Metal + acid → salt + hydrogen.
Why the others are wrong
(a) true, but only one of the three; (d) covers them all.
(b) true, but only one of the three; (d) covers them all.
(c) true, but only one of the three; (d) covers them all.
Remember
Dissolves, salt, hydrogen: all three.
Q7.4Arrhenius Concept
How many hydroxide ions will calcium hydroxide release in water?
Answer(b) 2
Step by step
The subscript 2 outside the bracket = two OH groups.
Why the others are wrong
(a) that is NaOH or KOH.
(c) it is a base, it gives OH⁻.
(d) that would be Al(OH)₃.
Remember
Count the OH groups.
Q7.5Reactions of Acids and Bases
In a neutralization reaction between KOH and H₃PO₄, how many molecules of KOH will react with one molecule of H₃PO₄?
Answer(c) 3
Step by step
3 H⁺ need 3 OH⁻.
Balanced: H₃PO₄ + 3KOH → K₃PO₄ + 3H₂O.
Why the others are wrong
(a) that gives K₂HPO₄, not full neutralisation.
(b) that gives KH₂PO₄.
(d) there are only three acidic H.
Remember
Acidic H count = KOH count.
Q7.6Acids, Bases and Alkalis
Which acid is used in the preparation of soap?
Answer(c) Stearic acid
Step by step
Fat/fatty acid + NaOH → soap (sodium stearate).
Why the others are wrong
(a) a fruit acid.
(b) a fruit acid.
(d) oxalic acid is not a fatty acid.
Remember
Soap = sodium stearate.
Q7.7Acid Rain
Which compound is formed when SO₂ is dissolved in water?
Answer(b) H₂SO₃
Step by step
SO₂ + H₂O → H₂SO₃.
SO₃ + H₂O → H₂SO₄.
Why the others are wrong
(a) SO₃ is another oxide, formed by oxidation.
(c) that comes from SO₃.
(d) oleum, made from SO₃ and H₂SO₄.
Remember
Same number of O plus one: SO₂ → H₂SO₃.
Q7.8Acids, Bases and Alkalis
Which of the following contains oxalic acid?
Answer(a) Tomato
Step by step
Match each source with its acid.
Why the others are wrong
(b) citric acid.
(c) tartaric acid.
(d) lactic acid.
Remember
Tomato–oxalic, tamarind–tartaric.
Q7.9Bronsted-Lowry Concept
Which compound in the reaction CH₃COOH + H₂O → CH₃COO⁻ + H₃O⁺ is behaving as a conjugate base?
Answer(c) CH₃COO⁻
Step by step
Acid CH₃COOH → conjugate base CH₃COO⁻.
Base H₂O → conjugate acid H₃O⁺.
Why the others are wrong
(a) it is the acid.
(b) it is the base.
(d) it is the conjugate acid.
Remember
Conjugate base = acid minus H⁺.
Q7.10Reactions of Acids and Bases
When a chemical reaction is carried out with a substance Z, a gas is produced which turns red litmus paper blue. What is the reaction?
Answer(d) Reaction of an alkali with ammonium salt
Step by step
Basic gas = NH₃.
NH₃ comes from alkali + ammonium salt.
Why the others are wrong
(a) that gives CO₂, which turns blue litmus faintly red.
(b) also CO₂.
(c) neutralisation gives salt and water, no gas.
Remember
Only basic gas in the syllabus: NH₃.
Set B: More MCQs from this chapter 14 MCQs
Extra questions on the same ideas, of the kind set in board papers and class tests.
QB1Acids, Bases and Alkalis
Acids change the colour of litmus paper from:
Answer(a) blue to red
Step by step
Acid: blue → red.
Why the others are wrong
(b) that is a base.
(c) Wrong.
(d) Wrong.
Remember
BRA: Blue to Red = Acid.
QB2Acids, Bases and Alkalis
An alkali is:
Answer(a) a base that dissolves in water
Step by step
All alkalis are bases; not all bases are alkalis.
Why the others are wrong
(b) many metal oxides are insoluble bases.
(c) Wrong.
(d) Wrong.
Remember
Alkali = soluble base.
QB3Acids, Bases and Alkalis
Which is a mineral acid?
Answer(c) Nitric acid
Step by step
Mineral: HCl, H₂SO₄, HNO₃.
Why the others are wrong
(a) organic, from lemons.
(b) organic, from sour milk.
(d) organic, in vinegar.
Remember
Mineral acids are the strong lab acids.
QB4Arrhenius Concept
According to Arrhenius, a base is a substance which in water gives:
Answer(a) OH⁻ ions
Step by step
Arrhenius acid → H⁺/H₃O⁺; base → OH⁻.
Why the others are wrong
(b) that is an acid.
(c) that is an acid.
(d) Wrong.
Remember
Base gives OH.
QB5Arrhenius Concept
H⁺ in water exists as H₃O⁺ because:
Answer(b) H⁺ is very small with a very high charge density and bonds to a lone pair of water
Step by step
A bare proton cannot exist free in water.
Why the others are wrong
(a) it is the smallest ion.
(c) water is polar.
(d) H⁺ is what acids donate.
Remember
Tiny + charged = grabs a lone pair.
QB6Strong and Weak Acids and Bases
A strong acid is one that:
Answer(d) ionises completely in water
Step by step
Strong = completely ionised.
Weak = partly ionised.
Why the others are wrong
(a) a weak acid can be concentrated too.
(b) all acids taste sour.
(c) that is a weak acid.
Remember
Strength ≠ concentration.
QB7Strong and Weak Acids and Bases
Which is a weak base?
Answer(c) NH₄OH
Step by step
NH₄OH ⇌ NH₄⁺ + OH⁻ (partial).
Why the others are wrong
(a) strong.
(b) strong.
(d) strong.
Remember
Ammonia water is weak.
QB8Strong and Weak Acids and Bases
Sulphuric acid ionises in water in two steps because it is:
Answer(b) diprotic
Step by step
Two acidic H atoms = diprotic = two steps.
Why the others are wrong
(a) HCl is monoprotic.
(c) it is a strong acid.
(d) Wrong.
Remember
Di = two protons.
QB9Bronsted-Lowry Concept
According to Bronsted-Lowry, a base is a:
Answer(a) proton acceptor
Step by step
Acid gives H⁺; base takes H⁺.
Why the others are wrong
(b) that is an acid.
(c) water is not needed.
(d) that is Arrhenius.
Remember
Base takes.
QB10Bronsted-Lowry Concept
Water is called amphoteric because it:
Answer(d) can act both as an acid and as a base
Step by step
HCl + H₂O → H₃O⁺ + Cl⁻ (water = base).
NH₃ + H₂O ⇌ NH₄⁺ + OH⁻ (water = acid).
Why the others are wrong
(a) neutral is not the reason.
(b) it ionises slightly.
(c) Wrong.
Remember
Ampho = both.
QB11Bronsted-Lowry Concept
Which is a Bronsted-Lowry base but not an Arrhenius base?
Answer(c) NH₃
Step by step
Arrhenius bases must contain OH⁻ to release.
Why the others are wrong
(a) both kinds.
(b) both kinds.
(d) both kinds.
Remember
No OH but still a base: NH₃.
QB12Reactions of Acids and Bases
Which metal does not evolve hydrogen with dilute acids?
Answer(d) Cu
Step by step
Reactive metals (Mg, Zn, Fe): salt + H₂.
Why the others are wrong
(a) reacts fast.
(b) Activity 7.2.
(c) gives H₂.
Remember
Coinage metals stay put.
QB13Reactions of Acids and Bases
Acids react with metal carbonates to give salt, water and:
Answer(a) CO₂
Step by step
Carbonate + acid → salt + water + CO₂.
Why the others are wrong
(b) Wrong.
(c) from metals.
(d) from ammonium salts with alkalis.
Remember
Fizz with a carbonate = CO₂.
QB14Acid Rain
The main gases responsible for acid rain are:
Answer(b) SO₂ and NO₂
Step by step
2SO₂ + O₂ → 2SO₃; SO₃ + H₂O → H₂SO₄.
2NO₂ + H₂O → HNO₂ + HNO₃.
Why the others are wrong
(a) CO₂ makes rain only slightly acidic; CO is not acidic.
