AS & A Level Chemistry - 9701 Paper 2 2022 Spring Zone 2

Fig. 1.1 shows how first ionisation energies vary across Period 2.


(a) Construct an equation to represent the first ionisation energy of oxygen. Include state symbols.
.................................................................................................................................................. [1]

(b) (i) State and explain the general trend in first ionisation energies across Period 2.
.................................................................................................................................................. [3]

(ii) Explain why ionisation energy A in Fig. 1.1 does not follow the general trend in first ionisation energies across Period 2.
................................................................................................................................. [2]

(c) Element E is in Period 3 of the Periodic Table. The first eight ionisation energy values of E are shown in Table 1.1.
[Table_1]

Deduce the full electronic configuration of E. Explain your answer.
full electronic configuration of E = ............................................................................
.................................................................................................................................
................................................................................................................................. [3]

Some oxides of elements in Period 3 are shown.

$\text{Na}_2\text{O}$\hspace{1cm}$\text{Al}_2\text{O}_3$\hspace{1cm}$\text{P}_4\text{O}_6$\hspace{1cm}$\text{P}_4\text{O}_{10}$\hspace{1cm}$\text{SO}_2$\hspace{1cm}$\text{SO}_3$

(a) Na reacts with $\text{O}_2$ to form $\text{Na}_2\text{O}$. Na is the reducing agent in this reaction.
(i) Define reducing agent.
\text{.................................................................................................................... [1]}
(ii) Write an equation for the reaction of $\text{Na}_2\text{O}$ with water.
\text{.................................................................................................................... [1]}

(b) $\text{Al}_2\text{O}_3$ is an amphoteric oxide found in bauxite.
(i) State what is meant by amphoteric.
\text{.................................................................................................................... [1]}
(ii) $\text{Al}_2\text{O}_3$ is purified from bauxite in several steps. The first step involves heating $\text{Al}_2\text{O}_3$ with an excess of $\text{NaOH(aq)}$. A colourless solution forms.
Write an equation for this reaction.
\text{.................................................................................................................... [1]}
(iii) $\text{Al}_2\text{O}_3$ is used as a catalyst in the dehydration of alcohols.
State the effect of using $\text{Al}_2\text{O}_3$ as a catalyst in the dehydration of alcohols. Use the Boltzmann distribution in Fig. 2.1 to help explain your answer.

\text{.................................................................................................................... [3]}

(c) $\text{P}_4\text{O}_6$ is a white solid that has a melting point of 24°C. Solid $\text{P}_4\text{O}_6$ reacts with water to form $\text{H}_3\text{PO}_3$.
(i) Deduce the type of structure and bonding shown by $\text{P}_4\text{O}_6$. Explain your answer.
\text{.................................................................................................................... [2]}
(ii) Determine the oxidation number of P in $\text{H}_3\text{PO}_3$.
\text{.................................................................................................................... [1]}
(iii) When $\text{P}_4\text{O}_6$(s) is heated with oxygen it forms $\text{P}_4\text{O}_{10}$(s).
$$\text{P}_4\text{O}_6(s) + 2\text{O}_2(g) \rightarrow \text{P}_4\text{O}_{10}(s) \hspace{1cm} \Delta H_{r} = -1372 \text{kJ mol}^{-1}$$
The enthalpy change of formation, $\Delta H_f$, of $\text{P}_4\text{O}_{10}$(s) is $-3012 \text{kJ mol}^{-1}$.
Calculate the enthalpy change of formation, $\Delta H_f$, of $\text{P}_4\text{O}_6$.
\[\Delta H_f \text{ of } \text{P}_4\text{O}_6(s) = \text{........................} \text{kJ mol}^{-1} [1]\]
(iv) Write an equation for the reaction of $\text{P}_4\text{O}_{10}$ with water.
\text{.................................................................................................................... [1]}

(d) $\text{SO}_2$ and $\text{SO}_3$ are found in the atmosphere.
The oxidation of $\text{SO}_2$ to $\text{SO}_3$ in the atmosphere is catalysed by $\text{NO}_2$.
The first step of the catalytic oxidation is shown in equation 1.

\[\text{equation 1}\hspace{0.5cm} \text{SO}_2(g) + \text{NO}_2(g) \rightleftharpoons \text{SO}_3(g) + \text{NO}(g)\]

(i) Construct an equation to show how $\text{NO}_2$ is regenerated in the catalytic oxidation of $\text{SO}_2$.
\text{.................................................................................................................... [1]}
(ii) $\text{NO}_2$ can also react with unburned hydrocarbons to form photochemical smog.
State the product of this reaction that contributes to photochemical smog.
\text{.................................................................................................................... [1]}
(iii) Fig. 2.2 shows how the temperature of the atmosphere varies with height from the ground.

The equilibrium reaction in equation 1 has $\Delta H_r = -168 \text{kJ mol}^{-1}$.
Suggest how the position of this equilibrium differs at a height of 20 km compared with a height of 50 km from the ground.
Explain your answer.
\text{.................................................................................................................... [2]}

The hydrogen halides HCl, HBr and HI are all colourless gases at room temperature.
(a) The hydrogen halides can be formed by reacting the halogens with hydrogen.
Describe and explain the relative reactivity of the halogens down the group when they react with hydrogen to form HCl, HBr and HI.
............................................................................................................................................. [2]

(b) HCl is a product of several different reactions. Some of these are shown in Fig. 3.1.

(i) Write an equation for reaction 1.
............................................................................................................................................... [1]
(ii) In reaction 2, NaCl reacts with concentrated $H_2SO_4$ to form $HCl$ and $NaHSO_4$. When $NaBr$ reacts with concentrated $H_2SO_4$, the products include $Br_2$ and $SO_2$.
Identify the type(s) of reaction that occur in each case by completing Table 3.1. Explain the difference in these reactions.
[Table_1]
explanation ............................................................................................................................... [3]

(c) When heated with a Bunsen burner, $HCl$ does not decompose, whereas $HI$ forms $H_2$ and $I_2$.
Explain the difference in the effect of heating on $HCl$ and $HI$.
............................................................................................................................................... [1]

(d) The hydrogen halides dissolve in water to form strong Brønsted–Lowry acids.
The concentration of a strong acid can be determined by titration.
(i) State what is meant by strong Brønsted–Lowry acid.
............................................................................................................................................... [2]
(ii) On Fig. 3.2, sketch the pH titration curves produced when:
• 0.1 mol dm$^{-3}$ $NaOH(aq)$ is added to 25 cm$^3$ of 0.1 mol dm$^{-3}$ $HBr(aq)$, to excess
• 0.1 mol dm$^{-3}$ $NH_3(aq)$ is added to 25 cm$^3$ of 0.1 mol dm$^{-3}$ $HBr(aq)$, to excess.

reaction of $NaOH(aq)$ and $HBr(aq)$
reaction of $NH_3(aq)$ and $HBr(aq)$ [3]

(e) $HBr$ reacts with propene to form two bromoalkanes, $CH_3CH_2CH_2Br$ and $(CH_3)_2CHBr$.
(i) Complete the diagram to show the mechanism of the reaction of $HBr$ and propene to form the major organic product. Include charges, dipoles, lone pairs of electrons and curly arrows, as appropriate. Draw the structures of the intermediate and the major organic product.

[4]
(ii) Explain why the two bromoalkanes are not produced in equal amounts by this reaction.
............................................................................................................................................... [2]
(iii) The reaction of $CH_3CH_2CH_2Br$ and $NaOH$ is different depending on whether water or ethanol is used as a solvent.
Complete Table 3.2 to identify the organic and inorganic products of the reaction of $CH_3CH_2CH_2Br$ and $NaOH$ in each solvent.
[Table_2]
[2]

Compounds J and K are found in plant oils.

[Image_1: Illustration of compounds J and K]

Fig. 4.1

(a) (i) Complete Table 4.1 to state what you would observe when J reacts with the reagents listed.

[Table_1]
| reagent | observation with J | |-------------------------|--------------------------| | 2,4-dinitrophenylhydrazine (2,4-DNPH) | | | Tollens’ reagent | | | sodium metal | |
[Marks: 3]

(ii) J has two optical isomers.
Draw the three-dimensional structures of the two optical isomers of J.
[Image_2: Placeholder for two optical isomers of J]
[Marks: 2]

(b) K is used to make the addition polymer Perspex®. A synthesis of Perspex® is shown in Fig. 4.2.

[Image_3: Synthesis of Perspex®]
Fig. 4.2

(i) Identify L. State the conditions required for reaction 1.
L = .................................................................
conditions = .................................................................
[Marks: 2]

(ii) Draw one repeat unit of the addition polymer Perspex®.
[Image_4: Placeholder for repeat unit of Perspex®]
[Marks: 2]

(iii) Use information from Table 4.2 to suggest how the infrared spectra of M and Perspex® would differ. Explain your answer.
.................................................................................................
[Table_2]
| bond | functional group containing the bond | characteristic infrared absorption range (in wavenumbers)/cm⁻¹ | |-----|--------------------------------------|-------------------------------------------------------| | C–O | hydroxy, ester | 1040–1300 | | C=C | aromatic compound, alkene | 1500–1680 | | C=O | amide carbonyl, carboxyl ester | 1640–1750 | | C≡N | nitrile | 2200–2250 | | C–H | alkane | 2850–3100 | | N–H | amine, amide | 3300–3500 | | O–H | carboxyl hydroxy | 2500–3650 |
[Marks: 1]

(iv) K can be made from propanone in the three-step synthesis shown in Fig. 4.3.

[Image_5: Three-step synthesis of K]
Fig. 4.3

Complete Table 4.3 to identify the reagent(s) used and the type of reaction in each step.

[Table_3]
| step | reagent(s) | type of reaction | |-----|----------------|------------------| | 1 | | | | 2 | | | | 3 | $Al_2O_3$ | |
[Marks: 5]