Grade 12 - Equilibria

The equilibrium constant, Kc, for the reaction to form ethyl ethanoate from ethanol and ethanoic acid,

C₂H₅OH + CH₃CO₂H → CH₃CO₂C₂H₅ + H₂O,

at 60^oC is 4.00.

When 1.00 mol each of ethanol and ethanoic acid are allowed to reach equilibrium at 60^oC, what is the number of moles of ethyl ethanoate formed?

• $\frac{1}{3}$

• $\frac{2}{3}$

• $\frac{1}{4}$

• $\frac{3}{4}$

Which of the following could act as buffer solutions?

• NaHCO₃ and Na₂CO₃

• CH₃CO₂H and NaCl

• HNO₃ and NaNO₃

• Ba(OH)₂ and BaCl₂

Which of the following can act as a Bronsted-Lowry acid?

• H₃O⁺

• OH^-

• CH₃COO^-

• NH₂^-

The pH of a 1.0 mol dm^-3 solution of a weak monobasic acid is 4. What is the dissociation constant of the weak acid?

• 1.0 x 10^-2 mol dm^-3

• 1.0 x 10^-4 mol dm^-3

• 1.0 x 10^-7 mol dm^-3

• 1.0 x 10^-8 mol dm^-3

An acidified solution containing 0.10 mol dm^-3 of zinc sulphate and 0.10 mol dm^-3 of copper(II) sulphate is saturated with hydrogen sulphide at 15^oC. The concentration of S^2-(aq) in the solution is then 10^-35 mol dm^-3.

The solubility product of zinc sulphide at 15^oC is 10^-24 mol² dm^-6 and of copper(II) sulphide is 10^-40 mol² dm^-6.

Which statement describes what happens in the solution?

• No precipitate is formed

• Copper(II) sulphide only is precipitated

• Copper(II) sulphide is precipitated first, followed by zinc sulphide

• Zinc sulphide is precipitated first, followed by copper(II) sulphide

Stomach juices have a pH of 1.0. aspirin is a monobasic acid represented by HA (Ka = 10^-4 mol dm^-3) which dissociation into ions H⁺ and A^-. What are the relative concentrations of H⁺, A^- and HA when aspirin from a tablet enters the stomach?

• [H⁺] > [HA] > [A^-]

• [HA] > [H⁺] = [A^-]

• [H⁺] > [A^-] > [HA]

• [H⁺] = [A^-] > [HA]

Which one of the following acid solution can be used to give an effective buffer solution at a pH < 7 by partial neutralization with aqueous NaOH?

• 0.01 mol dm^-3 CH₃CO₂H

• 0.1 mol dm^-3 HI

• 0.01 mol dm^-3 HCl

• 0.1 mol dm^-3 HNO₃

Which statement explains the observation that magnesium hydroxide dissolves in aqueous ammonium chloride, but not in aqueous sodium chloride?

• ionic radius of the NH₄⁺ ion is similar to that of Mg²⁺ but not that of Na⁺

• NH₄Cl dissociates less fully than NaCl.

• The ions Na⁺ and Mg²⁺ are isoelectronic (have the same number of electrons).

• The ion NH₄⁺ acts as an acid.

Why is ethanoic acid a stronger acid in liquid ammonia than in its aqueous solution

• ammonia is a stronger base than water

• ammonium ethanoate is completely ionized in aqueous solution

• ammonium ethanoate is strongly acidic in aqueous solution

• liquid ammonia is a more polar solvent than water

Which of the following shows the correct dissolution reaction for BaCl₂?

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Tags

NGSS.HS-PS1-3