Gaokao Exam Gaokao Chemistry: Chemical Equilibrium and Reactions 1

Question 1

For the equilibrium N₂(g) + 3H₂(g) ⇌ 2NH₃(g), increasing pressure at constant temperature will:

Accepted Answer

Shift the equilibrium toward products (NH₃)

Answer

By Le Chatelier's principle, increasing pressure favours the side with fewer moles of gas; the product side has 2 mol vs 4 mol reactants, so equilibrium shifts to products.

Question 2

The equilibrium constant expression for 2SO₂(g) + O₂(g) ⇌ 2SO₃(g) is:

Accepted Answer

K = [SO₃]²/([SO₂]²[O₂])

Answer

The equilibrium constant expression uses products over reactants, each raised to the power of the stoichiometric coefficient.

Question 3

At 25°C, for the reaction H₂(g) + I₂(g) ⇌ 2HI(g), K = 50. If [H₂] = [I₂] = 0.1 M and [HI] = 0.5 M initially, the reaction quotient Q is:

Accepted Answer

25

Answer

Q = [HI]²/([H₂][I₂]) = 0.25/(0.1 × 0.1) = 25. Since Q < K, the reaction proceeds forward.

Question 4

For an endothermic reaction at equilibrium, increasing temperature will:

Accepted Answer

Increase K and shift equilibrium toward products

Answer

For an endothermic reaction, heat is a 'reactant'; adding heat (increasing T) shifts equilibrium to the product side and increases K.

Question 5

Adding a catalyst to a reaction at equilibrium:

Accepted Answer

Speeds up both forward and reverse reactions equally, leaving equilibrium position unchanged

Answer

A catalyst lowers activation energy equally for forward and reverse reactions, reaching equilibrium faster but not changing K or the equilibrium position.

Gaokao Exam Practice Test

Gaokao Exam Practice Test

Gaokao Exam Gaokao Chemistry: Chemical Equilibrium and Reactions 1