AS & A Level Chemistry - 9701 Paper 2 2024 Winter Zone 2

Vanadium, niobium and tantalum are metals in the same group of the Periodic Table.
(a) The shorthand electronic configuration of vanadium in the ground state is $\text{[Ar]}3d^34s^2$.
(i) State what is meant by the term ground state.
............................................................................................................................................................................ [1]
(ii) Show the electronic configuration of vanadium using electrons in boxes notation.

[Ar] [ ] [ ] [ ] [ ] [ ]
[1]
(iii) Deduce the total number of electrons in the p sub-shells of a vanadium atom.
............................................................................................................................................................................ [1]
(b) Pelopium was the suggested name for a new element discovered in a mineral.
Pelopium was later found to be a mixture of niobium, Nb, and tantalum, Ta.
Only one naturally occurring isotope exists for each of Nb and Ta.
(i) Complete Table 1.1.

[Table_1]

Table 1.1
| isotope | relative isotopic mass | number of protons | number of neutrons |
|---------|------------------------|------------------|-------------------|
| $^{93}_{41}\text{Nb}$ | 92.91 | | |
| $^{181}_{73}\text{Ta}$ | 180.95 | | |

[2]
(ii) Define relative isotopic mass.
............................................................................................................................................................................ [2]
(iii) A sample of pelopium contains 90.9\% by mass $^{93}_{41}\text{Nb}$ and 9.1\% by mass $^{181}_{73}\text{Ta}$.
Calculate the theoretical relative atomic mass of pelopium based on these data and Table 1.1.
Give your answer to two decimal places.
Show your working.
theoretical relative atomic mass of pelopium = .............................. [2]
[Total: 9]

Oxygen is a Group 16 element.
(a) (i) Write equations for the following reactions.
• sodium and oxygen
• sulfur and oxygen
$\text{.............................................................................................................................}$ [2]
(ii) Draw a dot-and-cross diagram to show the species present in $\text{A}_2\text{O}_3$.
Draw outer electrons only.
[1]
(iii) The maximum oxidation state of the Period 3 elements in their oxides varies across the period.
State and explain the variation.
$\text{.............................................................................................................................}$ [2]
(b) $\text{H}_2\text{O}$ reacts with both inorganic and organic compounds.
(i) Complete Table 2.1 to give details of the reactions of some Period 3 oxides with $\text{H}_2\text{O}$.
\[\text{Table 2.1} \]
\[\begin{array}{|c|c|c|}\hline\text{Period 3 oxide} & \text{product of reaction} & \text{pH of solution formed} \\\hline\text{with H}_2\text{O} & & \\\hline\text{Mg(OH)}_2 & & \\\hline\text{P}_4\text{O}_{10} & & \\\hline\end{array} \]
[2]
(ii) Write an equation for the reaction of $\text{CH}_3\text{CN}$ with $\text{H}_2\text{O}$ in acidic conditions.
$\text{CH}_3\text{CN} + ......\text{H}_2\text{O} + ......\text{H}^+ ......$
$\text{..........................................................................................................}$ [1]
(iii) Draw the structures of the two alcohols formed in the reaction shown in equation 1.
equation 1 $\text{C}_3\text{H}_6(\text{g}) + \text{H}_2\text{O}(\text{g}) \xrightarrow{\text{H}_3\text{PO}_4} \text{C}_3\text{H}_8\text{O}(\text{g})$

[2]
(iv) Explain why alcohols are less acidic than water.
$\text{..........................................................................................................}$ [2]
(c) Fig. 2.1 shows the boiling points of $\text{H}_2\text{O}$ and other Group 16 hydrides.

(i) Explain the trend in the boiling points of the Group 16 hydrides $\text{H}_2\text{S}$ to $\text{H}_2\text{Te}$.
$\text{.................................................................................................................}$ [2]
(ii) Explain why the boiling point of $\text{H}_2\text{O}$ is much higher than that of $\text{H}_2\text{S}$.
$\text{.................................................................................................................}$ [1]
[Total: 15]

(a) Nitrogen is found in inorganic compounds such as nitrogen oxides (NO\(_x\)), nitrates and nitric acid.
(i) Identify one natural and one man-made occurrence of nitrogen oxides in the atmosphere.
natural .....................................................................................................................................
man-made ................................................................................................................................
[2]
(ii) Write an equation to describe the role of NO\(_2\) in the direct formation of acid rain.
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[1]
(iii) Peroxyacetyl nitrate, PAN, is a component of photochemical smog.
Describe how PAN forms from NO\(_2\).
..................................................................................................................................................
[1]
(iv) Nitric acid reacts with basic oxides to form nitrates.
Write an equation for the reaction of nitric acid with calcium oxide.
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[1]
(v) Describe what is seen when solid calcium nitrate is heated strongly.
..................................................................................................................................................
[1]

(b) A common test for nitrates is the reaction with NaOH and Al. Equation 1 shows the reaction.
equation 1 \(\ \ \ \ 3\text{NO}_3^- + 8\text{Al} + 5\text{OH}^- + 18\text{H}_2\text{O} \rightarrow 3\text{NH}_3 + 8[\text{Al(OH)}_4^-]\)
(i) Deduce the oxidation state of nitrogen in \(\text{NO}_3^-\).
..................................................................................................................................................
[1]
(ii) Identify the species that is oxidised in equation 1.
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[1]
(iii) \(\text{NH}_3\) is a basic gas.
Describe how \(\text{NH}_3\) is able to act as a base.
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[1]
(iv) Suggest the shape of the \([\text{Al(OH)}_4^-]\) ion.
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[1]

(c) Fig. 3.1 shows a sketch of some of the ionisation energies of phosphorus, P.


(i) Construct an equation to represent the third ionisation energy of P.
..................................................................................................................................................
[1]
(ii) Complete the graph in Fig. 3.1 to show the third to sixth ionisation energies of P.
[2]

(d) Complete Table 3.1 to show the properties of nitrogen and phosphorus in their standard states.
[Table_1]

Table 3.1
\[\begin{array}{|c|c|c|}\hline \text{ } & \text{nitrogen} & \text{phosphorus} \\ \hline \text{state and appearance of standard state} & \text{colourless gas} & \text{white solid} \\ \hline \text{electrical conductivity} & & \text{poor} \\ \hline \text{type of bonding} & & \\ \hline \text{type of structure} & \text{simple} & \\ \hline\end{array}\]
[2]

(e) A form of solid nitrogen has a lattice structure similar to solid iodine.
Identify the type of lattice structure of solid nitrogen.
..................................................................................................................................................
[1]

(f) At very high temperatures, phosphorus can form \(\text{P}_2\) molecules.
\(\text{P}_2\) contains a triple bond, \(\text{P}\equiv\text{P}\).
(i) Describe the formation of the \(\text{P}\equiv\text{P}\) bond in terms of orbital overlap.
..................................................................................................................................................
[2]
(ii) The bond energy of \(\text{P}\equiv\text{P}\) is 485 kJ mol\(^{-1}\). The bond energy of \(\text{N}\equiv\text{N}\) is 944 kJ mol\(^{-1}\).
Compare the reactivity of \(\text{P}_2\) and \(\text{N}_2\). Explain your answer.
..................................................................................................................................................
[1]

(a) Complete Fig. 4.2 to show the mechanism for the formation of 1,2-dibromoethane in reaction 1.

Include charges, dipoles, lone pairs of electrons and curly arrows as appropriate.
$$\text{H}_2\text{C}=\text{CH}_2 \rightarrow \text{Br}\hspace{0.1cm}\text{CH}_2\text{CH}_2\hspace{0.1cm}\text{Br}$$

(b) The enthalpy change of reaction 1, $\Delta H_r = -90.0 \text{kJ mol}^{-1}$.

The enthalpy change of formation of ethene, $\Delta H_f = +52.2 \text{kJ mol}^{-1}$.

Calculate the enthalpy change of formation of 1,2-dibromoethane.

$\Delta H_f$ of 1,2-dibromoethane = ....................... $\text{kJ mol}^{-1}$ [1]

(c) (i) Complete Fig. 4.1 to:
- draw the structure of compound A
- name compound B.
[2]
(ii) Draw the structure of one repeat unit of polymer C in the box.
[1]
(iii) In reaction 5, compound B reacts with an excess of NaOH dissolved in ethanol. The products are HBr, $\text{H}_2\text{O}$ and an unsaturated hydrocarbon D.
Suggest the identity of D.
............................................................. [1]

(d) Compound E is the only isomer of 1,2-dibromoethane.
Alkaline hydrolysis of E gives compound F.


(i) Identify the type of isomerism shown by E and 1,2-dibromoethane.
............................................................. [1]

(ii) Name the homologous series that F belongs to.
............................................................. [1]

(iii) Complete Table 4.1 to state what is observed when F reacts with the reagents listed.


(e) Compound F reacts with reagent G to form compound H.
The infrared spectrum of H is shown in Fig. 4.3.

H also shows a molecular ion peak at $\text{m}/\text{e} = 60$ in its mass spectrum.

(i) Use the information in (e), Fig. 4.3 and Table 4.2 to deduce the structure of H. Explain your answer fully.
............................................................. [3]

(ii) Suggest the role of reagent G.
............................................................. [1]

[Total: 17]