Chemistry 9701 · AS & A Level · Group 2

Group 2 — practice question

(a(i))[4]

Describe how the solubility of the hydroxides of magnesium, calcium and strontium varies. Explain your answer. Arrange them from most soluble to least soluble.

(a(ii))[1]

Suggest how the pH of saturated solutions of the hydroxides of magnesium, calcium and strontium changes. Explain your answer.

(b)[4]

Barium hydroxide, $\text{Ba(OH)}_2$, is a strong base. A $250.0\,\text{cm}^3$ solution of $\text{Ba(OH)}_2$ with pH $12.2$ is prepared by dissolving $\text{Ba(OH)}_2$ in distilled water. Calculate the mass of $\text{Ba(OH)}_2$ needed to prepare this solution. Show your working. [$M_r$ of $\text{Ba(OH)}_2 = 171.3$]

(c(i))[1]

At $298\,\text{K}$, the solubility of iron(II) hydroxide, $\text{Fe(OH)}_2$, is $5.85 \times 10^{-6}\,\text{mol dm}^{-3}$. Write the expression for the solubility product, $K_{sp}$, of $\text{Fe(OH)}_2$.

(c(ii))[2]

Calculate the value of $K_{sp}$ for $\text{Fe(OH)}_2$. State its units.

Worked solution & mark scheme

This 12-mark question has a full step-by-step worked solution and mark scheme. One marking point: Sequence: strontium > calcium > magnesium

  • Full mark scheme, point by point
  • Step-by-step worked solution
  • Write your answer & get it marked instantly by AI