Chemistry 9701 · AS & A Level · 3.1

3.1 — practice question

Group 17 elements behave as oxidising agents.
(a(i))[1]

Explain how the Group 17 elements act as oxidising agents.

(a(ii))[1]

Write an equation to show the reaction in which $\text{Cl}_2$ oxidises aluminium metal.

(a(iii))[1]

A student heats equal amounts of $\text{I}_2(g)$ and $\text{H}_2(g)$ in a sealed flask, then allows the contents to cool. State what you observe during the reaction.

(b(i))[2]

Both $\text{Cl}_2$ and $\text{Br}_2$ react with $\text{NH}_3$ to form $\text{N}_2$ and a hydrogen halide, HX. $3\text{X}_2 + 2\text{NH}_3 \rightarrow \text{N}_2 + 6\text{HX}$, where $\text{X} = \text{Cl}$ or $\text{Br}$. The relative bond strengths of X-X and H-X are what make the enthalpy changes of the two reactions different. Describe and explain the difference in the X-X bond strengths of $\text{Cl}_2$ and $\text{Br}_2$.

(b(ii))[1]

Describe the relative thermal stabilities of HCl and HBr.

(b(iii))[2]

Define enthalpy change of formation, $\Delta H_f$.

(b(iv))[2]

Table 1.1 supplies data relevant to the reaction of $\text{Cl}_2(g)$ with $\text{NH}_3(g)$. Use the data in Table 1.1 to calculate the enthalpy change of the reaction of $\text{Cl}_2(g)$ with $\text{NH}_3(g)$. Give your answer in $\text{kJ mol}^{-1}$.

(b(v))[2]

When $\text{I}_2$ reacts with $\text{NH}_3$, $\text{NI}_3$ is formed. Predict the shape of a molecule of $\text{NI}_3$. Explain your answer.

(c(i))[4]

Complete Table 1.2.

(c(ii))[2]

Suggest an identity for the species that produces each observation in the reaction of NaI with concentrated $\text{H}_2\text{SO}_4$. black solid; yellow solid; effervescence.

(d(i))[2]

Table 1.3 provides some information about $\text{MgCl}_2$ and $\text{SiCl}_4$. Explain the difference between the electrical conductivity of liquid $\text{MgCl}_2$ and of liquid $\text{SiCl}_4$. Refer to bonding and relevant particles in your answer.

(d(ii))[2]

Suggest the pH of the solutions that form when each chloride is added to water. $\text{MgCl}_2$ ________ $\text{SiCl}_4$ ________

Worked solution & mark scheme

This 22-mark question has a full step-by-step worked solution and mark scheme. One marking point: (halogens can) withdraw electron(s) from a reactant

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