Equilibria - exam practice

When magnesium hydroxide dissolves in water, the following equilibrium is established.

Mg(OH)_2(s) ⇌ Mg²⁺_(aq) + 2OH^-_(aq)

The expression for the is solubility product, K_sp

The solubility product of magnesium hydroxide, Mg(OH)₂, is 2.00 × 10^-11 mol³ dm^-9.

What is the solubility of magnesium hydroxide, in mol dm^-3?

A solution of hydrochloric acid has pH = 2.

The solution is diluted to one tenth of its original concentration.

What is the pH of the diluted solution?

When equimolar amounts of the solutions below are mixed, which forms a buffer solution with a pH less than 7?

The indicator methyl orange is a weak acid and may be represented by the formula HA_(aq). The equation for its dissociation is shown below.

HA_(aq) ⇌. A^- + H⁺(aq)

Colour: Red Yellow

Under certain conditions, at equilibrium, a solution of HA has a yellow colour.

On addition of a small volume of dilute sodium hydroxide, the colour of this solution would

20 cm³ of 0.10 mol dm^-3 hydrochloric acid is added to 10 cm³ of 0.10 mol dm^-3 sodium hydroxide.

What is the pH of the resulting mixture?

The equation shows the dissociation of the acid H₃AsO₄ in water.

H3AsO₄ + H₂O ⇌ H₂AsO₄^- + H₃O⁺

Which pair is a conjugate acid–base pair?

A buffer solution is prepared by mixing 200 cm³ of 2.00 mol dm^-3 propanoic acid, CH₃CH₂COOH, with 600 cm³ of 1.00 mol dm^-3 sodium propanoate, CH₃CH₂COONa.

K_a for CH₃CH₂COOH = 1.32 × 10^-5 mol dm^-3

What is the pH of the buffer solution?

2,4,6-Trichlorophenol is a weak monoprotic acid, with K_a = 2.51 × 10^-8 mol dm^-3 at 298 K.

What is the concentration, in mol dm^-3, of hydrogen ions in a 2.00 × 10^-3 mol dm^-3 solution of 2,4,6-trichlorophenol at 298 K?

What is the pH of a 0.46 mol dm^-3 solution of potassium hydroxide at 298 K?

K_w = 1.0 × 10^-14 mol² dm^-6 at 298 K.

The diagram shows a pH curve produced by adding a strong alkali to a weak acid.

Which point on the curve represents a solution that can act as a buffer?

The acid dissociation constant, K_a, of a weak acid HA has the value 2.56 × 10^-4 mol dm^-3

What is the pH of a 4.25 × 10^-3 mol dm^-3 solution of HA?

A 0.10 mol dm^-3 aqueous solution of an acid is added slowly to 25 cm³ of a 0.10 mol dm^-3 aqueous solution of a base.

Which acid–base pair has the highest pH at the equivalence point?

Which is the concentration of NaOH_(aq), in mol dm^-3, that has pH = 14.30?

K_w = 1.00 × 10^-14 mol² dm^-6 at 25°C

What is the pH of 0.015 mol dm^-3 sulfuric acid?

A buffer solution always...