A Level Chemistry 9701 Paper 21, May/June 2025

Solid sodium conducts electricity. Sodium oxide conducts electricity when molten but not when solid. Name the type of bonding present in sodium and in sodium oxide. bonding in sodium ............................................................................................................. bonding in sodium oxide ...................................................................................................

Explain how solid sodium conducts electricity.

Explain why sodium oxide conducts electricity when molten.

Separate samples of sodium and sodium oxide are each added to an excess of cold water. Write an equation for the reaction of sodium with cold water.

Write an equation for the reaction of sodium oxide with cold water.

Complete Table 1.1. Do not refer to temperature changes when considering observations for these reactions. Table 1.1

State the oxidation number of the Period 3 elements bonded to $\mathrm{C}\mathrm{l}$ in $\mathrm{N}\mathrm{a}\mathrm{C}\mathrm{l}$ and ${\mathrm{P}\mathrm{C}\mathrm{l}}_5$. Explain the difference in the oxidation number.

Table 1.2 shows melting points of some oxides. Table 1.2

A student suggests the following hypothesis. The higher the oxidation number of the element combined with oxygen, the higher the melting point of the oxide. Use Table 1.2 to deduce if this hypothesis is true or false or if there is not enough information to make a conclusion. Explain your answer.

Define isotopes.

Fig. 2.1 shows the mass spectrum of the sample of iron. Use Fig. 2.1 to calculate the relative atomic mass, $A_{\mathrm{r}}$, of iron to one decimal place. Show your working. $A_{\mathrm{r}}\text{ of iron}=\text{..............................}$

Complete Table 2.1 to show the number of protons and nucleons in one atom of ${}^{56}\mathrm{F}\mathrm{e}$. Table 2.1

Deduce the number of pairs of electrons in the shell with principal quantum number $n=3$ in an $\mathrm{F}\mathrm{e}$ atom. number of pairs of electrons ..............................

Write an equation to represent the first ionisation energy of iron.

Suggest how the value for the first ionisation energy of ${}^{54}\mathrm{F}\mathrm{e}$ compares to the first ionisation energy of ${}^{56}\mathrm{F}\mathrm{e}$. Explain your answer in terms of the factors that affect ionisation energy.

Hexene reacts with hydrogen gas to produce hexane. $$\text{reaction 1}{\mathrm{C}}_6{\mathrm{H}}_{12}(\mathrm{l})+{\mathrm{H}}_2(\mathrm{g})\to {\mathrm{C}}_6{\mathrm{H}}_{14}(\mathrm{l})$$ Fig. 3.1 shows the distribution of energies of ${\mathrm{H}}_2(\mathrm{g})$ molecules at temperature $T$. Sketch on Fig. 3.1 the shape of the curve for the same sample of ${\mathrm{H}}_2(\mathrm{g})$ molecules when the temperature is increased.

Explain why increasing the temperature increases the rate of reaction 1.

State the role of nickel when it is added to reaction 1.

Annotate Fig. 3.2 to show the effect of adding nickel to reaction 1 at temperature $T$.

Define Le Chatelier’s principle.

Reaction 2 shows the equilibrium reaction between $\mathrm{X}(\mathrm{g})$ and $\mathrm{Y}(\mathrm{g})$ to produce $\mathrm{Z}(\mathrm{g})$ in a sealed container. $$\text{reaction 2}a\mathrm{X}(\mathrm{g})+b\mathrm{Y}(\mathrm{g})\rightleftharpoons c\mathrm{Z}(\mathrm{g})$$ Fig. 3.3 shows the effect of changing pressure on the percentage yield of $\mathrm{Z}(\mathrm{g})$ at two different temperatures, $300\mathrm{K}$ and $350\mathrm{K}$. Deduce two conclusions about reaction 2 using Fig 3.3.

Deduce the empirical formula of vitamin C.

The concentration of vitamin C is found by titration with ${\mathrm{I}}_2(\mathrm{a}\mathrm{q})$. A vitamin C tablet is dissolved in water to produce $200.0{\mathrm{c}\mathrm{m}}^3$ of vitamin C solution. $5.00{\mathrm{c}\mathrm{m}}^3$ of this vitamin C solution is added to a flask with approximately $150{\mathrm{c}\mathrm{m}}^3$ of water and an indicator. Exactly $28.40{\mathrm{c}\mathrm{m}}^3$ of $5.00\times {10}^{-4}\mathrm{m}\mathrm{o}\mathrm{l}{\mathrm{d}\mathrm{m}}^{-3}{\mathrm{I}}_2(\mathrm{a}\mathrm{q})$ reacts with the sample of vitamin C solution in the flask. [$M_{\mathrm{r}}$: vitamin C, 176] Calculate the amount, in mol, of ${\mathrm{I}}_2(\mathrm{a}\mathrm{q})$ added to the flask in this titration. $\text{amount of }{\mathrm{I}}_2(\mathrm{a}\mathrm{q})=\text{..............................mol}$

Use your answer to (b)(i) to calculate the mass, in g, of vitamin C in the tablet. Show your working. (If you were unable to calculate a value for the amount of ${\mathrm{I}}_2(\mathrm{a}\mathrm{q})$ in (b)(i), use the value $2.64\times {10}^{-4}\mathrm{m}\mathrm{o}\mathrm{l}$. This is not the correct value.) $\text{mass of vitamin C in tablet}=\text{..............................g}$

Deduce the role of ${\mathrm{I}}_2(\mathrm{a}\mathrm{q})$ in the reaction in Fig. 4.2.

Suggest two reasons why hot concentrated acidified potassium manganate(VII) is not a suitable reagent for producing Q from vitamin C. 1 ........................................................................................................................................ ........................................................................................................................................... 2 ........................................................................................................................................ ...........................................................................................................................................

Predict two absorptions that will be seen in the infrared spectra of both vitamin C and Q. Describe the relevant bond and the specific functional group that is responsible for each absorption identified.

Draw the structure of A.

Name the type of reaction that occurs when A is heated with ${\mathrm{H}}_2{\mathrm{S}\mathrm{O}}_4(\mathrm{a}\mathrm{q})$.

When aqueous ${\mathrm{N}\mathrm{a}}_2{\mathrm{C}\mathrm{O}}_3$ is added to separate samples of B and C, effervescence is observed with B only. Complete the equation to describe the reaction between B and an excess of aqueous ${\mathrm{N}\mathrm{a}}_2{\mathrm{C}\mathrm{O}}_3$. ......${\mathrm{H}\mathrm{O}\mathrm{O}\mathrm{C}\mathrm{C}\mathrm{H}}_2\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H}$ + ......${\mathrm{N}\mathrm{a}}_2{\mathrm{C}\mathrm{O}}_3\to$ .............................................................................

Suggest why C does not react with aqueous ${\mathrm{N}\mathrm{a}}_2{\mathrm{C}\mathrm{O}}_3$ in a similar type of reaction to B.

A student suggests a two-step synthesis to produce B, as shown in Fig. 5.2. Identify the reagents and conditions required in steps 1 and 2. step 1 ................................................................................................................ step 2 ................................................................................................................

Identify the type of reaction that ${\mathrm{H}\mathrm{O}\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_2{\mathrm{C}\mathrm{H}}_2\mathrm{O}\mathrm{H}$ undergoes in step 2.

B reacts with an excess of reducing agent R to produce D. An excess of ${\mathrm{P}\mathrm{C}\mathrm{l}}_5$ is added to D. • A vigorous reaction occurs. • Misty fumes are seen. • Organic compound E is produced. Identify the formula of the reducing agent R.

Complete the equation to describe the reaction of B with an excess of R. Use $[\mathrm{H}]$ to represent one atom of hydrogen from R. ......${\mathrm{H}\mathrm{O}\mathrm{O}\mathrm{C}\mathrm{C}\mathrm{H}}_2\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H}$ + ......$[\mathrm{H}]\to$ ...............................................................................

Name organic compound E.

State the functional group in ethanal, propanal and propanone.

State a reagent and the relevant observation that confirm that F, G and H have the same functional group. reagent ..................................................................................................................................... observation ...............................................................................................................................

Separate samples of F, G and H are each tested with Tollens’ reagent and with alkaline ${\mathrm{I}}_2(\mathrm{a}\mathrm{q})$. The observations are shown in Table 6.1. Table 6.1

Use Table 6.1 to name the organic compounds in bottles F, G and H. F = ............................................. G = ............................................. H = .............................................

Identify the yellow precipitate produced when alkaline ${\mathrm{I}}_2(\mathrm{a}\mathrm{q})$ is added to separate samples of F and G.

Compound J does not contain the same functional group as F, G and H. Compound J also reacts with alkaline ${\mathrm{I}}_2(\mathrm{a}\mathrm{q})$ to produce a pale yellow precipitate. Suggest the structure of compound J.