Chemistry 9701/42 — October/November 2015

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

questions

100

marks

120

minutes

Topics Introduction to A Level Organic Chemistry · Transition Elements · Nitrogen Compounds · Chemical Energetics · Group 2 · Analytical Techniques · +4 more

Q1Group 2Chemical EnergeticsFree sample

(a)

Calcium has atomic number 20.

Complete the electronic structures for a

calcium atom, $1s^2 2s^2 2p^6$ .................................

calcium ion in the +2 oxidation state. $1s^2 2s^2 2p^6$ .................................

(b)

Calcium nitrate, $\text{Ca(NO}_3)_2$ , is used in fertilisers and can be prepared by an acid-base reaction.

Write an equation for the preparation of calcium nitrate by an acid-base reaction.

(c)

(i)

When anhydrous calcium nitrate is heated strongly, it decomposes to leave a white solid.

Identify this white solid and suggest another observation for this reaction.

(ii)

The ease of thermal decomposition of the Group II nitrates decreases down the group.

Explain this trend.

(d)

(i)

What is meant by the term standard enthalpy change of hydration, $\Delta H^\ominus_{\text{hyd}}$ ?

(ii)

Use the following data to calculate the lattice energy, $\Delta H^\ominus_{\text{latt}}$ , of calcium nitrate, $\text{Ca(NO}_3)_2(\text{s})$ .

You may find it helpful to construct an energy cycle.

enthalpy change	value
$\Delta H^\ominus_{\text{hyd}} (\text{Ca}^{2+}(\text{g}))$	$-1650 \text{ kJ mol}^{-1}$
$\Delta H^\ominus_{\text{hyd}} (\text{NO}_3^-(\text{g}))$	$-314 \text{ kJ mol}^{-1}$
enthalpy change of solution for $\text{Ca(NO}_3)_2(\text{s})$	$-19 \text{ kJ mol}^{-1}$

\Delta H^\ominus_{\text{latt}} \text{ Ca(NO}_3)_2(\text{s}) = \text{........................... kJ mol}^{-1}

(e)

The standard enthalpy change of hydration for $\text{Ba}^{2+}$ , $\Delta H^\ominus_{\text{hyd}}(\text{Ba}^{2+}(\text{g}))$ , is $-1305 \text{ kJ mol}^{-1}$ .

Suggest an explanation for why the $\Delta H^\ominus_{\text{hyd}}$ of the $\text{Ba}^{2+}$ ion is less exothermic than the $\Delta H^\ominus_{\text{hyd}}$ of the $\text{Ca}^{2+}$ ion.

The rest of this paper

9 more questions

Q2Transition Elements · Group 27M
Q3Transition Elements9M
Q4Introduction to A Level Organic Chemistry · Reaction Kinetics9M
Q5Electrochemistry11M
Q6Chemical Energetics · Introduction to A Level Organic Chemistry · Organic Synthesis10M
Q7Nitrogen Compounds · Introduction to A Level Organic Chemistry12M
Q8Nitrogen Compounds · Introduction to A Level Organic Chemistry · Chemical Energetics · Analytical Techniques10M
Q9Transition Elements · Nitrogen Compounds · Analytical Techniques11M
Q10Introduction to A Level Organic Chemistry · Nitrogen Compounds · Carboxylic Acids and Derivatives · Transition Elements9M

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