Chemistry 9701 · AS & A Level · Group 2

Group 2 — practice question

Oxygen is the Earth’s crust’s most plentiful element. It combines with other elements to produce stable compounds, ions and molecules.
(a)[2]

Fill in the table with the formulae and acid/base behaviour for some oxides of the Period 3 elements.

(b(i))[1]

Beryllium hydroxide, $\text{Be(OH)}_2$, is an amphoteric compound that shows chemical reactions similar to aluminium oxide. State what the term amphoteric means.

(b(ii))[1]

Write an ionic equation for the reaction between magnesium hydroxide, $\text{Mg(OH)}_2$, and hydrochloric acid.

(b(iii))[1]

Two methods of making strontium hydroxide are shown. State one difference between the observations you would make for reaction 1 and reaction 2.

(b(iv))[1]

State how the solubility of the Group 2 hydroxides changes down the group.

(c(i))[2]

Sodium peroxide, $\text{Na}_2\text{O}_2$, reacts with $\text{CO}_2$. $\text{Na}_2\text{O}_2(s) + \text{CO}_2(g) \rightarrow \text{Na}_2\text{CO}_3(s) + \tfrac{1}{2}\text{O}_2(g)$. The partial pressure of $\text{CO}_2(g)$ in a $0.500\,\text{dm}^3$ air sample is $5.37\,\text{kPa}$ at $20^\circ\text{C}$. Calculate the amount, in moles, of $\text{CO}_2(g)$ present in the air sample at $20^\circ\text{C}$.

(c(ii))[1]

Calculate the mass of $\text{Na}_2\text{O}_2(s)$ that would react completely with the amount of $\text{CO}_2(g)$ calculated in (i).

(c(iii))[2]

The peroxide ion, $\text{O}_2^{2-}$, has a single covalent bond between the two oxygen atoms. Each oxygen atom carries a negative charge. Draw a ‘dot-and-cross’ diagram for the peroxide ion. Show outer electrons only.

Worked solution & mark scheme

This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: Correct formulae: $\ce{Na2O}$, $\ce{Al2O3}$, $\ce{SiO2}$, $\ce{P4O10 / P4O6 / P2O3 / P2O5}$, $\ce{SO3}$

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