[Maximum number: 1]

Two groups of students (Group A and Group B) carried out a project* on the chemistry of some group 7 elements (the halogens) and their compounds.

(a)

In the first part of the project, the two groups had a sample of iodine monochloride (a corrosive brown liquid) prepared for them by their teacher using the following reaction.

\mathrm{I}_{2}(\mathrm{~s})+\mathrm{Cl}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{ICl}(\mathrm{l})

The following data were recorded.

[ 1 ]

(i)

Using a digital thermometer, the students discovered that the reaction was exothermic. State the sign of the enthalpy change of the reaction, $\Delta H$ .

[ 1 ]

[Maximum number: 1]

Two groups of students (Group A and Group B) carried out a project* on the chemistry of some group 7 elements (the halogens) and their compounds.

(a)

In the first part of the project, the two groups had a sample of iodine monochloride (a corrosive brown liquid) prepared for them by their teacher using the following reaction.

\mathrm{I}_{2}(\mathrm{~s})+\mathrm{Cl}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{ICl}(\mathrm{l})

The following data were recorded.

[ 1 ]

(i)

Using a digital thermometer, the students discovered that the reaction was exothermic. State the sign of the enthalpy change of the reaction, $\Delta H$ .

[ 1 ]

(a)

Magnesium sulfate can exist in either the hydrated form or in the anhydrous form. Two students wished to determine the enthalpy of hydration of anhydrous magnesium sulfate. They measured the initial and the highest temperature reached when anhydrous magnesium sulfate, $\mathrm{MgSO}_{4}(\mathrm{~s})$ , was dissolved in water. They presented their results in the following table.

[ 2 ]

(i)

Calculate the enthalpy change, $\Delta H_{1}$ , for anhydrous magnesium sulfate dissolving in water, in $\mathrm{kJ} \mathrm{mol}^{-1}$ . State your answer to the correct number of significant figures.

[ 2 ]

(a)

Two chemistry students wished to determine the enthalpy of hydration of anhydrous magnesium sulfate. They measured the initial and the highest temperature reached when anhydrous magnesium sulfate, $\mathrm{MgSO}_{4}(\mathrm{~s})$ , was dissolved in water. They presented their results in the table below.

[ 2 ]

(i)

Calculate the enthalpy change, $\Delta H_{1}$ , for anhydrous magnesium sulfate dissolving in water, in $\mathrm{kJ} \mathrm{mol}^{-1}$ . State your answer to the correct number of significant figures.

[ 2 ]

[Maximum number: 4]

A student carried out an experiment to determine the concentration of a hydrochloric acid solution and the enthalpy change of the reaction between aqueous sodium hydroxide and this acid by thermometric titration.

She added $5.0 \mathrm{~cm}^{3}$ portions of hydrochloric acid to $25.0 \mathrm{~cm}^{3}$ of $1.00 \mathrm{moldm}^{-3}$ sodium hydroxide solution in a glass beaker until the total volume of acid added was $50.0 \mathrm{~cm}^{3}$ , measuring the temperature of the mixture each time. Her results are plotted in the graph below.

The initial temperature of both solutions was the same.

(a)

(i)

Determine the change in temperature, $\Delta T$ .

[ 1 ]

(ii)

Calculate the enthalpy change, in $\mathrm{kJ} \mathrm{mol}^{-1}$ , for the reaction of hydrochloric acid and sodium hydroxide solution.

[ 3 ]

[Maximum number: 3]

A student carried out an experiment to determine the concentration of a hydrochloric acid solution and the enthalpy change of the reaction between aqueous sodium hydroxide and this acid by thermometric titration.

She added $5.0 \mathrm{~cm}^{3}$ portions of hydrochloric acid to $25.0 \mathrm{~cm}^{3}$ of $1.00 \mathrm{moldm}^{-3}$ sodium hydroxide solution in a glass beaker until the total volume of acid added was $50.0 \mathrm{~cm}^{3}$ , measuring the temperature of the mixture each time. Her results are plotted in the graph below.

The initial temperature of both solutions was the same.

(a)

(i)

Calculate the enthalpy change, in $\mathrm{kJ} \mathrm{mol}^{-1}$ , for the reaction of hydrochloric acid and sodium hydroxide solution.

[ 3 ]

[Maximum number: 1]

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})

[ 1 ]

(i)

The enthalpy change, $\Delta H^{\ominus}$ , for the following similar reaction is -233.8 kJ .

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

Deduce why this value differs from your answer to (a)(iii).

[ 1 ]

[Maximum number: 1]

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)

(i)

Deduce why the answers to (a)(iii) and (b)(i) differ.

[ 1 ]

[Maximum number: 4]

A student titrated an ethanoic acid solution, $\mathrm{CH}_{3} \mathrm{COOH}(\mathrm{aq})$ , against $50.0 \mathrm{~cm}^{3}$ of $0.995 \mathrm{~mol} \mathrm{dm}^{-3}$ sodium hydroxide, NaOH(aq), to determine its concentration.
The temperature of the reaction mixture was measured after each acid addition and plotted against the volume of acid.

(a)

(i)

Determine the heat change, q, in kJ , for the neutralization reaction between ethanoic acid and sodium hydroxide.
Assume the specific heat capacities of the solutions and their densities are those of water.

[ 2 ]

(ii)

Calculate the enthalpy change, $\Delta H$ , in $\mathrm{kJ} \mathrm{mol}^{-1}$ , for the reaction between ethanoic acid and sodium hydroxide.

[ 2 ]

[Maximum number: 4]

A student titrated two acids, hydrochloric acid, HCl(aq) and ethanoic acid, $\mathrm{CH}_{3} \mathrm{COOH}(\mathrm{aq})$ , against $50.0 \mathrm{~cm}^{3}$ of $0.995 \mathrm{~mol} \mathrm{dm}^{-3}$ sodium hydroxide, NaOH(aq), to determine their concentration. The temperature of the reaction mixture was measured after each acid addition and plotted against the volume of each acid.

(a)

(i)

Determine the heat change, q, in kJ , for the neutralization reaction between ethanoic acid and sodium hydroxide.
Assume the specific heat capacities of the solutions and their densities are those of water.

[ 2 ]

(ii)

Calculate the enthalpy change, $\Delta H$ , in $\mathrm{kJ} \mathrm{mol}^{-1}$ , for the reaction between ethanoic acid and sodium hydroxide.

[ 2 ]