All 24 MCQs of 9th Class Chemistry Chapter 6, Equilibria, 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 6 in your book, in the book's option order.
Q6.1Dynamic Equilibrium
What will happen if the rates of forward and reverse reactions are very high?
Answer(a) The equilibrium point will reach very soon.
Step by step
Time to equilibrium depends on the speed of the reactions.
Fast both ways → equilibrium soon.
Why the others are wrong
(b) slow reactions take long (even years).
(c) a reversible reaction in a closed vessel always reaches equilibrium.
(d) a high backward rate means the reaction clearly goes both ways.
Remember
Fast reactions = quick equilibrium.
Q6.2Temperature and Pressure
Predict which components of the atmosphere react in the presence of lightning.
Answer(d) N₂ and O₂
Step by step
N₂ + O₂ ⇌ 2NO, highly endothermic.
Why the others are wrong
(a) N₂ does not react with water vapour here.
(b) O₂ and water give no reaction.
(c) CO₂ cannot burn further.
Remember
Lightning makes NO.
Q6.3Dynamic Equilibrium
An inorganic chemist places one mole of PCl₅ in container A and one mole of each of Cl₂ and PCl₃ in container B. Both containers were sealed and heated to the same temperature to reach equilibrium. Guess about the composition of the mixtures in both containers.
Answer(a) Both the containers will have the same composition of mixtures.
Step by step
A: PCl₅ → PCl₃ + Cl₂ until the rates are equal.
B: PCl₃ + Cl₂ → PCl₅ until the rates are equal.
Same atoms, same volume, same temperature: same mixture.
Why the others are wrong
(b) both end with the same amount of PCl₃.
(c) see (b).
(d) a reversible reaction never uses up its reactants; all three are present.
Remember
Equilibrium can be approached from either side.
Q6.4Reversible and Irreversible Reactions
CaO or lime is used extensively in steel, glass and paper industries. It is produced in a reversible reaction by the decomposition of limestone (CaCO₃). Choose the conditions to produce maximum amount of lime.
Answer(b) Heating at high temperature in an open vessel
Step by step
High temperature: the decomposition (endothermic) takes place.
Open vessel: CO₂ escapes, so the backward reaction cannot happen.
Why the others are wrong
(a) in a closed vessel CO₂ reacts with CaO to give back CaCO₃: only an equilibrium mixture.
(c) limestone does not decompose without heating.
(d) no decomposition without heat.
Remember
Let the gas escape.
Q6.5Dynamic Equilibrium
What condition should be met for the reversible reaction to achieve the state of equilibrium?
Answer(c) The concentrations of all the reactants and the products should become constant.
Step by step
Rate forward = rate backward.
Concentrations constant.
Why the others are wrong
(a) a reversible reaction never goes to completion.
(b) there is no fixed 50 %; the position depends on the reaction and conditions.
(d) removing a product disturbs the equilibrium and drives the reaction forward.
Remember
Constant, not equal and not complete.
Q6.6Temperature and Pressure
Why does the gas start coming out when you open a can of fizzy drink?
Answer(c) Because the gas is dissolved under pressure, hence it comes out when pressure is decreased
Step by step
High pressure → more gas dissolves.
Pressure released → gas comes out.
Why the others are wrong
(a) solubility decreases when the pressure falls.
(b) CO₂ is fairly soluble, especially under pressure.
(d) solubility of a gas increases at high pressure.
Remember
Release the pressure, release the gas.
Q6.7Temperature and Pressure
The reaction CaCO₃(s) ⇌ CaO(s) + CO₂(g) is performed in a closed vessel. How will the equilibrium be affected if you increase the pressure?
Answer(b) The backward reaction will be favoured
Step by step
Gas moles: left 0, right 1.
High pressure favours fewer gas moles → backward.
Why the others are wrong
(a) forward makes more gas.
(c) the backward reaction is favoured.
(d) the gas moles differ, so pressure matters.
Remember
Count gas moles only; solids do not count.
Q6.8Reversible and Irreversible Reactions
When will a reaction become a reversible one?
Answer(a) If the activation energy of the forward reaction is comparable to that of backward reaction
Step by step
Comparable Eₐ both ways: both reactions happen.
Very different Eₐ: one direction dominates.
Why the others are wrong
(b) then the products return easily and few products remain; it is not the condition for reversibility in general.
(c) a much lower forward barrier makes the reaction practically one-way.
(d) the enthalpy changes of forward and backward reactions are equal and opposite, not both zero.
Remember
Equal hills both sides = two-way traffic.
Q6.9Catalyst and Industry
Are reversible reactions useful for preparing compounds on a large scale?
Answer(b) Yes
Step by step
Disturb the equilibrium in favour of the product (remove it, change T or P).
Recycle unreacted reactants.
Why the others are wrong
(a) the Haber process is a reversible reaction used industrially.
(c) the Haber equilibrium does not lie far to the right, yet it is used, by removing ammonia.
(d) an equilibrium far to the left gives little product.
Remember
Haber process = yes.
Q6.10Dynamic Equilibrium
What will happen to the concentrations of the products if a reversible reaction at equilibrium is not disturbed?
Answer(a) They will remain constant
Step by step
Forward rate = backward rate, for ever, if undisturbed.
Why the others are wrong
(b) that happens only before equilibrium.
(c) that would need a disturbance.
(d) no change without a disturbance.
Remember
Undisturbed equilibrium never changes.
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.
