(a)

The students repeated the experiment using 6.16 g of solid hydrated magnesium sulfate, $\mathrm{MgSO}_{4} \cdot 7 \mathrm{H}_{2} \mathrm{O}(\mathrm{s})$ , and $50.0 \mathrm{~cm}^{3}$ of water. They found the enthalpy change, $\Delta H_{2}$ , to be $+18 \mathrm{~kJ} \mathrm{~mol}^{-1}$ .

The enthalpy of hydration of solid anhydrous magnesium sulfate is difficult to determine experimentally, but can be determined using the diagram below.

\mathrm{MgSO}_{4} \cdot 7 \mathrm{H}_{2} \mathrm{O}(\mathrm{~s}) \xrightarrow[\text { water }]{\Delta H_{2}} \mathrm{Mg}^{2+}(\mathrm{aq})+\mathrm{SO}_{4}^{2-}(\mathrm{aq})

[ 1 ]

(i)

Determine the enthalpy change, $\Delta H$ , in $\mathrm{kJ} \mathrm{mol}^{-1}$ , for the hydration of solid anhydrous magnesium sulfate, $\mathrm{MgSO}_{4}$ .

[ 1 ]

(a)

The students repeated the experiment using 6.16 g of solid hydrated magnesium sulfate, $\mathrm{MgSO}_{4} \cdot 7 \mathrm{H}_{2} \mathrm{O}(\mathrm{s})$ , and $50.0 \mathrm{~cm}^{3}$ of water. They found the enthalpy change, $\Delta H_{2}$ , to be $+18 \mathrm{~kJ} \mathrm{~mol}^{-1}$ .

The enthalpy of hydration of solid anhydrous magnesium sulfate is difficult to determine experimentally, but can be determined using the diagram below.

[ 1 ]

(i)

Determine the enthalpy change, $\Delta H$ , in $\mathrm{kJ} \mathrm{mol}^{-1}$ , for the hydration of solid anhydrous magnesium sulfate, $\mathrm{MgSO}_{4}$ .

[ 1 ]

[Maximum number: 3]

Ethane-1,2-diol, $\mathrm{HOCH}_{2} \mathrm{CH}_{2} \mathrm{OH}$ , has a wide variety of uses including the removal of ice from aircraft and heat transfer in a solar cell.

(a)

Ethane-1,2-diol can be formed according to the following reaction.

2 \mathrm{CO}(\mathrm{~g})+3 \mathrm{H}_{2}(\mathrm{~g}) \rightleftharpoons \mathrm{HOCH}_{2} \mathrm{CH}_{2} \mathrm{OH}(\mathrm{~g})

[ 3 ]

(i)

Calculate the enthalpy change, $\Delta H^{\ominus}$ , in kJ , for this reaction using section 11 of the data booklet. The bond enthalpy of the carbon-oxygen bond in CO(g) is $1077 \mathrm{~kJ} \mathrm{~mol}^{-1}$ .

[ 3 ]

[Maximum number: 4]

Ethane-1,2-diol, $\mathrm{HOCH}_{2} \mathrm{CH}_{2} \mathrm{OH}$ , has a wide variety of uses including the removal of ice from aircraft and heat transfer in a solar cell.

(a)

Ethane-1,2-diol can be formed according to the following reaction.

2 \mathrm{CO}(\mathrm{~g})+3 \mathrm{H}_{2}(\mathrm{~g}) \rightleftharpoons \mathrm{HOCH}_{2} \mathrm{CH}_{2} \mathrm{OH}(\mathrm{~g})

[ 3 ]

(i)

Calculate the enthalpy change, $\Delta H^{\ominus}$ , in kJ , for this reaction using section 11 of the data booklet. The bond enthalpy of the carbon-oxygen bond in CO(g) is $1077 \mathrm{~kJ} \mathrm{~mol}^{-1}$ .

[ 3 ]

(b)

(i)

Calculate $\Delta H^{\ominus}$ , in kJ , for this similar reaction below using $\Delta H_{\mathrm{f}}^{\ominus}$ data from section 12 of the data booklet. $\Delta H_{\mathrm{f}}^{\ominus}$ of $\mathrm{HOCH}_{2} \mathrm{CH}_{2} \mathrm{OH}(\mathrm{l})$ is $-454.8 \mathrm{~kJ} \mathrm{~mol}^{-1}$ .

2 \mathrm{CO}(\mathrm{~g})+3 \mathrm{H}_{2}(\mathrm{~g}) \rightleftharpoons \mathrm{HOCH}_{2} \mathrm{CH}_{2} \mathrm{OH}(\mathrm{l})

[ 1 ]

[Maximum number: 3]

Ethyne, $\mathrm{C}_{2} \mathrm{H}_{2}$ , reacts with oxygen in welding torches.

(a)

Ethyne reacts with steam.

Two possible products are:

[ 3 ]

(i)

Determine the enthalpy change for the reaction, in kJ , to produce A using section 11 of the data booklet.

[ 3 ]

[Maximum number: 3]

Ethyne, $\mathrm{C}_{2} \mathrm{H}_{2}$ , reacts with oxygen in welding torches.

(a)

Ethyne reacts with steam.

\mathrm{C}_{2} \mathrm{H}_{2}(\mathrm{~g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{~g}) \rightarrow \mathrm{C}_{2} \mathrm{H}_{4} \mathrm{O}(\mathrm{~g})

Two possible products are:

[ 3 ]

(i)

Determine the enthalpy change for the reaction, in kJ , to produce A using section 11 of the data booklet.

[ 3 ]

[Maximum number: 2]

Limestone can be converted into a variety of useful commercial products through the lime cycle. Limestone contains high percentages of calcium carbonate, $\mathrm{CaCO}_{3}$ .

(a)

Thermodynamic data for the decomposition of calcium carbonate is given.

Calculate the enthalpy change of reaction, $\Delta H$ , in kJ , for the decomposition of calcium carbonate.

[ 2 ]

[Maximum number: 2]

Ammonium nitrate, $\mathrm{NH}_{4} \mathrm{NO}_{3}$ , is used as a high nitrogen fertilizer.

(a)

Solid ammonium nitrate can decompose to gaseous dinitrogen monoxide and liquid water.

[ 2 ]

(i)

Calculate the standard enthalpy change, $\Delta H^{\ominus}$ , of the reaction. Use section 12 of the data booklet.

\begin{aligned} & \Delta H_{\mathrm{f}}^{\ominus} \text { ammonium nitrate }=-366 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ & \Delta H_{\mathrm{f}}^{\ominus} \text { dinitrogen monoxide }=82 \mathrm{~kJ} \mathrm{~mol}^{-1} \end{aligned}

[ 2 ]

[Maximum number: 2]

Ammonium nitrate, $\mathrm{NH}_{4} \mathrm{NO}_{3}$ , is used as a high nitrogen fertilizer.

(a)

Solid ammonium nitrate can decompose to gaseous dinitrogen monoxide and liquid water.

[ 2 ]

(i)

Calculate the standard enthalpy change, $\Delta H^{\ominus}$ , of the reaction. Use section 12 of the data booklet.

\begin{aligned} & \Delta H_{\mathrm{f}}^{\ominus} \text { ammonium nitrate }=-366 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ & \Delta H_{\mathrm{f}}^{\ominus} \text { dinitrogen monoxide }=82 \mathrm{~kJ} \mathrm{~mol}^{-1} \end{aligned}

[ 2 ]

[Maximum number: 1]

White phosphorus is an allotrope of phosphorus and exists as $\mathrm{P}_{4}$ .

(a)

An equilibrium exists between $\mathrm{PCl}_{3}$ and $\mathrm{PCl}_{5}$ .

\mathrm{PCl}_{3}(\mathrm{~g})+\mathrm{Cl}_{2}(\mathrm{~g}) \rightleftharpoons \mathrm{PCl}_{5}(\mathrm{~g})

[ 1 ]

(i)

Calculate the standard enthalpy change $\left(\Delta H^{\ominus}\right)$ for the forward reaction in $\mathrm{kJ} \mathrm{mol}^{-1}$ .

\begin{aligned} & \Delta H^{\ominus}{ }_{\mathrm{f}} \mathrm{PCl}_{3}(\mathrm{~g})=-306.4 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ & \Delta H^{\ominus}{ }_{\mathrm{f}} \mathrm{PCl}_{5}(\mathrm{~g})=-398.9 \mathrm{~kJ} \mathrm{~mol}^{-1} \end{aligned}

[ 1 ]