Gaokao Exam Gaokao Chemistry: Chemical Equilibrium and Reactions 2

Question 1

In the Haber process N₂ + 3H₂ ⇌ 2NH₃ (ΔH = −92 kJ/mol), which conditions maximise yield of NH₃?

Accepted Answer

High pressure, low temperature

Answer

High pressure favours fewer moles of gas (products); low temperature favours the exothermic forward reaction thermodynamically (though kinetics require compromise).

Question 2

The common ion effect refers to:

Accepted Answer

The decrease in solubility or dissociation when an ion in common with the equilibrium is added

Answer

Adding a common ion shifts the equilibrium toward the undissociated or insoluble form, decreasing dissociation or solubility.

Question 3

For a reaction with K >> 1, the equilibrium position lies:

Accepted Answer

Far to the right, heavily favouring products

Answer

K >> 1 means [products] >> [reactants] at equilibrium; the reaction essentially goes to completion.

Question 4

The pH of a 0.01 M HCl solution at 25°C is:

Accepted Answer

2

Answer

HCl is a strong acid, fully dissociated: [H⁺] = 0.01 M; pH = −log(0.01) = 2.

Question 5

In a buffer solution made from CH₃COOH and CH₃COO⁻, adding a small amount of strong acid causes:

Accepted Answer

The base component (CH₃COO⁻) to neutralise the acid, minimising pH change

Answer

Buffer action: added H⁺ reacts with the conjugate base CH₃COO⁻ → CH₃COOH, consuming the extra acid and stabilising pH.

Gaokao Exam Practice Test

Gaokao Exam Practice Test

Gaokao Exam Gaokao Chemistry: Chemical Equilibrium and Reactions 2