(a)

The major source of sulfur for the manufacture of sulfuric acid by the Contact process is the de-sulfurisation of 'sour' natural gas. Many natural gas wells produce a mixture of volatile hydrocarbons (mainly $\mathrm{CH}_{4}$ and $\mathrm{C}_{2} \mathrm{H}_{6}$ ) together with up to 25 % hydrogen sulfide, $\mathrm{H}_{2} \mathrm{~S}$ .

[ 8 ]

(i)

Use the following data to calculate $\Delta H^{\ominus}$ for the reaction between $\mathrm{H}_{2} \mathrm{~S}$ and $\mathrm{SO}_{2}$ .

$\mathrm{kJ} \mathrm{mol}^{-1}$

[ 8 ]

[Maximum number: 2]

Sulfides are compounds that contain sulfur but not oxygen.

(a)

The enthalpy change of combustion of $\mathrm{CS}_{2}(\mathrm{I})$ is represented by the following equation.

\mathrm{CS}_{2}(\mathrm{l})+3 \mathrm{O}_{2}(\mathrm{~g}) \xrightarrow{\Delta H_{\mathrm{c}}} \mathrm{CO}_{2}(\mathrm{~g})+2 \mathrm{SO}_{2}(\mathrm{~g})

[ 2 ]

(i)

The table shows the enthalpy changes of formation of $\mathrm{CS}_{2}(\mathrm{I}), \mathrm{CO}_{2}(\mathrm{~g})$ and $\mathrm{SO}_{2}(\mathrm{~g})$ .

Use the data in the table to calculate the enthalpy change of combustion, $\Delta H_{\mathrm{c}}$ , of $\mathrm{CS}_{2}(\mathrm{I})$ , in $\mathrm{kJ} \mathrm{mol}{ }^{-1}$ .

Show your working.
$\Delta H_{\mathrm{c}}$ of $\mathrm{CS}_{2}(\mathrm{I})=$ $\mathrm{kJ} \mathrm{mol}^{-1}$

[ 2 ]

[Maximum number: 12]

Hydrazine, $\mathrm{N}_{2} \mathrm{H}_{4}$ , can be used as a rocket fuel and is stored as a liquid. It reacts exothermically with oxygen to give only gaseous products.

The enthalpy change of a reaction such as that between hydrazine and oxygen may be calculated by using standard enthalpy changes of formation.

(a)

Hydrazine reacts with oxygen according to the following equation.

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

(i)

Use the data in the table to calculate the standard enthalpy change of this reaction.

\Delta H^{\ominus}=

$\mathrm{kJ} \mathrm{mol}^{-1}$

[Maximum number: 1]

Group 2 metals form alkaline solutions in water.

(a)

Magnesium peroxide, $\mathrm{MgO}_{2}$ , is made in the following reaction.

\mathrm{MgO}(\mathrm{~s})+\mathrm{H}_{2} \mathrm{O}_{2}(\mathrm{l}) \rightarrow \mathrm{MgO}_{2}(\mathrm{~s})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \quad \Delta H=-96 \mathrm{~kJ} \mathrm{~mol}^{-1}

[ 1 ]

(i)

Magnesium peroxide decomposes slowly to form magnesium oxide and oxygen.

\mathrm{MgO}_{2}(\mathrm{~s}) \rightarrow \mathrm{MgO}(\mathrm{~s})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g})

Use your answer to (g)(iii) and the data in the table to calculate the enthalpy change of this reaction.

If you were unable to obtain an answer to (g)(iii), use the value $\Delta H_{\mathrm{f}}=-550 \mathrm{~kJ} \mathrm{~mol}^{-1}$ . This is not the correct answer.
enthalpy change of reaction = $\mathrm{kJ} \mathrm{mol}^{-1}$

[ 1 ]

[Maximum number: 1]

The enthalpy change of formation of carbon dioxide is $-394 \mathrm{~kJ} \mathrm{~mol}^{-1}$ .
The enthalpy change of formation of water is $-286 \mathrm{~kJ} \mathrm{~mol}^{-1}$ .
The enthalpy change of formation of methane is $-74 \mathrm{~kJ} \mathrm{~mol}^{-1}$ .
What is the enthalpy change of combustion of methane?

A

$-892 \mathrm{~kJ} \mathrm{~mol}^{-1}$

B

$-606 \mathrm{~kJ} \mathrm{~mol}^{-1}$

C

$+606 \mathrm{~kJ} \mathrm{~mol}^{-1}$

D

$+892 \mathrm{~kJ} \mathrm{~mol}^{-1}$

[Maximum number: 1]

A student performed an experiment to measure the enthalpy change of combustion of ethane.
He used the following values for the standard enthalpy changes of combustion of carbon and hydrogen.

\begin{aligned} & \Delta H_{\mathrm{c}}^{\ominus} \text { carbon }=-394 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ & \Delta H_{\mathrm{c}}^{\ominus} \text { hydrogen }=-286 \mathrm{~kJ} \mathrm{~mol}^{-1} \end{aligned}

He calculated the enthalpy change of formation of ethane to be $-140 \mathrm{~kJ} \mathrm{~mol}^{-1}$ .
What was his experimental value for the standard enthalpy change of combustion of ethane?

A

$-2364 \mathrm{~kJ} \mathrm{~mol}^{-1}$

B

$-1506 \mathrm{~kJ} \mathrm{~mol}^{-1}$

C

$-1112 \mathrm{~kJ} \mathrm{~mol}^{-1}$

D

$-540 \mathrm{~kJ} \mathrm{~mol}^{-1}$

[Maximum number: 1]

Enthalpy changes that are difficult to measure directly can often be determined using Hess' Law to construct an enthalpy cycle.

Which enthalpy change is indicated by X in the enthalpy cycle shown?

A

$-4 \times$ the enthalpy of combustion of hydrogen

B

$+4 \times$ the enthalpy of combustion of hydrogen

C

$-2 \times$ the enthalpy of formation of water

D

$+2 \times$ the enthalpy of formation of water

[Maximum number: 1]

$\Delta H_{1}^{\ominus}$ is the standard enthalpy of formation of methane.
$\Delta H_{2}^{\ominus}$ is the standard enthalpy of combustion of carbon.
$\Delta H_{3}^{\ominus}$ is the standard enthalpy of combustion of hydrogen.

Which expression is equivalent to $\Delta H_{\mathrm{c}}^{\ominus}$ ?

A

$\Delta H_{1}^{\ominus}-\Delta H_{2}^{\ominus}+\Delta H_{3}^{\ominus}$

B

$\Delta H_{1}^{\ominus}-2 \Delta H_{3}^{\ominus}-\Delta H_{2}^{\ominus}$

C

$\Delta H_{2}^{\ominus}-\Delta H_{3}^{\ominus}+\Delta H_{1}^{\ominus}$

D

$\Delta H_{2}^{\ominus}+2 \Delta H_{3}^{\ominus}-\Delta H_{1}^{\ominus}$

[Maximum number: 1]

The following data are needed for this question.

\begin{array}{cl} \mathrm{NaHCO}_{3}(\mathrm{~s})+\mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{NaCl}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l})+\mathrm{CO}_{2}(\mathrm{~g}) & \Delta H=-38.97 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ \mathrm{Na}_{2} \mathrm{CO}_{3}(\mathrm{~s})+2 \mathrm{HCl}(\mathrm{aq}) \rightarrow 2 \mathrm{NaCl}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l})+\mathrm{CO}_{2}(\mathrm{~g}) & \Delta H=-96.59 \mathrm{~kJ} \mathrm{~mol}^{-1} \end{array}

On heating, sodium hydrogencarbonate decomposes as shown.

2 \mathrm{NaHCO}_{3}(\mathrm{~s}) \rightarrow \mathrm{Na}_{2} \mathrm{CO}_{3}(\mathrm{~s})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l})+\mathrm{CO}_{2}(\mathrm{~g})

What is the enthalpy change for this decomposition?

A

$-57.62 \mathrm{~kJ} \mathrm{~mol}^{-1}$

B

$-18.65 \mathrm{~kJ} \mathrm{~mol}^{-1}$

C

$18.65 \mathrm{~kJ} \mathrm{~mol}^{-1}$

D

$57.62 \mathrm{~kJ} \mathrm{~mol}^{-1}$

[Maximum number: 1]

Propanone has the molecular formula $\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}$ .
The enthalpy change of combustion of hydrogen is $-286 \mathrm{~kJ} \mathrm{~mol}^{-1}$ .
The enthalpy change of combustion of carbon is $-394 \mathrm{~kJ} \mathrm{~mol}^{-1}$ .
The enthalpy change of combustion of propanone is $-1786 \mathrm{~kJ} \mathrm{~mol}^{-1}$ .
Using this information, what is the enthalpy change of formation of propanone?

A

$-1106 \mathrm{~kJ} \mathrm{~mol}^{-1}$

B

$-540 \mathrm{~kJ} \mathrm{~mol}^{-1}$

C

$-254 \mathrm{~kJ} \mathrm{~mol}^{-1}$

D

$+1106 \mathrm{~kJ} \mathrm{~mol}^{-1}$

Question 1

Question 1(b)

Question 1(b)(v)

Question 1

Question 1(b)

Question 1(b)(ii)

Question 1

Question 1(b)

Question 1(b)(i)

Question 1

Question 1(g)

Question 1(g)(iv)

Question 3

Question 3

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Question 5