Chemistry 9701/41 — May/June 2018

Cambridge A-Level · A Level Structured Questions · worked solutions for every part, with the mark scheme

questions

100

marks

120

minutes

Topics Group 2 · Introduction to A Level Organic Chemistry · Chemical Energetics · Equilibria · Reaction Kinetics · Electrochemistry · +6 more

Q1Chemical EnergeticsEquilibriaFree sample

Sodium oxide, $\text{Na}_2\text{O}$ , is a white crystalline solid with a high melting point.

(a)

Write an equation for the reaction of sodium with oxygen, forming sodium oxide.
Include state symbols.

(b)

Explain why sodium oxide has a high melting point.

(c)

When sodium oxide reacts with water an alkaline solution is obtained.

(i)

Explain why the solution obtained is alkaline. You should use the Brønsted-Lowry theory of acids and bases in your answer.

(ii)

Calculate the pH of the solution obtained when $3.10\text{ g}$ of sodium oxide are added to $400\text{ cm}^3$ of water.

\text{pH} = \text{..............................}

(d)

Use the data below, and other suitable data from the Data Booklet, to calculate the lattice energy of sodium oxide, $\Delta H_{\text{latt}}^{\ominus}$ $\text{Na}_2\text{O(s)}$ .

energy change	value / $\text{kJ mol}^{-1}$
standard enthalpy change of formation of sodium oxide, $\Delta H_{\text{f}}^{\ominus}$ $\text{Na}_2\text{O(s)}$	$-416$
standard enthalpy change of atomisation of sodium, $\Delta H_{\text{at}}^{\ominus}$ $\text{Na(s)}$	$+109$
electron affinity of $\text{O(g)}$	$-142$
electron affinity of $\text{O}^-\text{(g)}$	$+844$

\Delta H_{\text{latt}}^{\ominus} \text{ Na}_2\text{O(s)} = \text{............................................ kJ mol}^{-1}

(e)

State how $\Delta H_{\text{latt}}^{\ominus}$ $\text{Na}_2\text{S(s)}$ differs from $\Delta H_{\text{latt}}^{\ominus}$ $\text{Na}_2\text{O(s)}$ .
Indicate this by placing a tick ( $\checkmark$ ) in the appropriate box in the table.

$\Delta H_{\text{latt}}^{\ominus}$ $\text{Na}_2\text{S(s)}$ is more exothermic than $\Delta H_{\text{latt}}^{\ominus}$ $\text{Na}_2\text{O(s)}$	$\Delta H_{\text{latt}}^{\ominus}$ $\text{Na}_2\text{S(s)}$ is the same as $\Delta H_{\text{latt}}^{\ominus}$ $\text{Na}_2\text{O(s)}$	$\Delta H_{\text{latt}}^{\ominus}$ $\text{Na}_2\text{S(s)}$ is less exothermic than $\Delta H_{\text{latt}}^{\ominus}$ $\text{Na}_2\text{O(s)}$

Explain your answer.

The rest of this paper

8 more questions

Q2Reaction Kinetics · Group 214M
Q3Electrochemistry11M
Q4Group 27M
Q5Transition Elements17M
Q6Hydrocarbons13M
Q7Hydroxy Compounds · Carboxylic Acids and Derivatives · Analytical Techniques12M
Q8Introduction to A Level Organic Chemistry6M
Q9Introduction to A Level Organic Chemistry · Nitrogen Compounds5M

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