2024 Cambridge IAS-Level Chemistry (9701) Practice Paper with Answers

A sample of \( 1.97\text{ g} \) of a carbonate of a Group 2 metal, \( \text{XCO}_3 \), is thermally decomposed to completion. \( \text{XCO}_3(s) \rightarrow \text{XO}(s) + \text{CO}_2(g) \) The carbon dioxide gas produced occupies \( 240\text{ cm}^3 \) at room temperature and pressure (r.t.p.). What is the identity of the Group 2 metal, \( \text{X} \)? (Assume 1 mole of gas occupies \( 24.0\text{ dm}^3 \) at r.t.p.)

A student reacts \( 4.00\text{ g} \) of copper(II) oxide with excess dilute sulfuric acid to prepare copper(II) sulfate crystals, \( \text{CuSO}_4 \cdot 5\text{H}_2\text{O} \). \( \text{CuO}(s) + \text{H}_2\text{SO}_4(aq) \rightarrow \text{CuSO}_4(aq) + \text{H}_2\text{O}(l) \) Upon crystallization and drying, the student obtains \( 10.0\text{ g} \) of hydrated copper(II) sulfate, \( \text{CuSO}_4 \cdot 5\text{H}_2\text{O} \). What is the percentage yield of the hydrated copper(II) sulfate? [Relative atomic masses: \( \text{H} = 1.0 \), \( \text{O} = 16.0 \), \( \text{S} = 32.1 \), \( \text{Cu} = 63.5 \)]

Consider the following standard enthalpy changes: \( 2\text{C}(s) + 3\text{H}_2(g) \rightarrow \text{C}_2\text{H}_6(g) \quad \Delta H^\theta = -84.7\text{ kJ mol}^{-1} \) ; \( \text{C}(s) + \text{O}_2(g) \rightarrow \text{CO}_2(g) \quad \Delta H^\theta = -393.5\text{ kJ mol}^{-1} \) ; \( \text{H}_2(g) + \frac{1}{2}\text{O}_2(g) \rightarrow \text{H}_2\text{O}(l) \quad \Delta H^\theta = -285.8\text{ kJ mol}^{-1} \). What is the standard enthalpy change of combustion of ethane, \( \text{C}_2\text{H}_6(g) \)?

In a calorimetry experiment, \( 50.0\text{ cm}^3 \) of \( 1.00\text{ mol dm}^{-3} \) aqueous sodium hydroxide is mixed with \( 50.0\text{ cm}^3 \) of \( 1.00\text{ mol dm}^{-3} \) hydrochloric acid in a polystyrene cup. Both solutions were initially at \( 20.2\text{ }^\circ\text{C} \). After mixing, the temperature rose to a maximum of \( 26.8\text{ }^\circ\text{C} \). Assume the density of the solution is \( 1.00\text{ g cm}^{-3} \) and its specific heat capacity is \( 4.18\text{ J g}^{-1}\text{ K}^{-1} \). What is the enthalpy change of neutralisation, \( \Delta H_n \), for this reaction?

Four separate samples of Period 3 oxides are added to water and the pH of the resulting mixture is measured. The oxides tested are: \( \text{Na}_2\text{O} \), \( \text{Al}_2\text{O}_3 \), \( \text{P}_4\text{O}_{10} \), and \( \text{SO}_3 \). Which sequence correctly ranks these oxides in order of increasing pH of their aqueous mixtures?

Which physical property of the Period 3 elements (sodium to argon) increases to a maximum value at silicon, and then decreases sharply to phosphorus?

An equilibrium mixture is established in a \( 2.0\text{ dm}^3 \) sealed container at a constant temperature according to the following equation: \( 2\text{SO}_2(g) + \text{O}_2(g) \rightleftharpoons 2\text{SO}_3(g) \) At equilibrium, the mixture contains \( 0.40\text{ mol} \) of \( \text{SO}_2 \), \( 0.20\text{ mol} \) of \( \text{O}_2 \), and \( 1.60\text{ mol} \) of \( \text{SO}_3 \). What is the value of the equilibrium constant, \( K_c \), at this temperature?

The industrial synthesis of ammonia is represented by the following equilibrium: \( \text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g) \quad \Delta H = -92\text{ kJ mol}^{-1} \) Which combination of changes will both decrease the equilibrium yield of ammonia and decrease the value of the equilibrium constant, \( K_p \)?

Propan-1-ol, \(\text{C}_3\text{H}_7\text{OH}(l)\), can be formed from its elements according to the following equation:

\[ 3\text{C}(s) + 4\text{H}_2(g) + \frac{1}{2}\text{O}_2(g) \rightarrow \text{C}_3\text{H}_7\text{OH}(l) \]

The standard enthalpies of combustion, \(\Delta H_c^\ominus\), for carbon, hydrogen, and propan-1-ol are given in the table below.

| Substance | \(\Delta H_c^\ominus\text{ / kJ mol}^{-1}\) |
|---|---|
| \(\text{C}(s)\) | \(-394\) |
| \(\text{H}_2(g)\) | \(-286\) |
| \(\text{C}_3\text{H}_7\text{OH}(l)\) | \(-2021\) |

What is the standard enthalpy change of formation, \(\Delta H_f^\ominus\), of propan-1-ol?

A sample of \(1.20\text{ g}\) of a mixture containing anhydrous calcium carbonate, \(\text{CaCO}_3\) (\(M_r = 100.1\)), and sodium chloride, \(\text{NaCl}\), reacts completely with excess dilute hydrochloric acid. The volume of \(\text{CO}_2\) gas collected at room temperature and pressure (r.t.p.) is \(180\text{ cm}^3\).

What is the percentage by mass of \(\text{CaCO}_3\) in the sample?

(Assume 1.00 mol of gas occupies \(24.0\text{ dm}^3\) under r.t.p. conditions).

Three Period 3 elements, \(X\), \(Y\), and \(Z\), have oxides with the following properties:

- The oxide of \(X\) is insoluble in water but dissolves in both dilute aqueous sodium hydroxide and dilute hydrochloric acid.
- The oxide of \(Y\) reacts violently with water to form a strongly acidic solution of pH 1–2.
- The oxide of \(Z\) dissolves in water to form a strongly alkaline solution of pH 13–14.

Which sequence correctly identifies the elements \(X\), \(Y\), and \(Z\)?

A mixture of \(\text{SO}_2(g)\) and \(\text{O}_2(g)\) is allowed to reach equilibrium in a closed vessel of fixed volume according to the equation:

\[ 2\text{SO}_2(g) + \text{O}_2(g) \rightleftharpoons 2\text{SO}_3(g) \quad \Delta H = -197\text{ kJ mol}^{-1} \]

The temperature of the system is increased while the volume is kept constant. Which statement correctly describes the change in the value of the equilibrium constant, \(K_c\), and the rate of the reverse reaction?

The equation for the complete combustion of methanal, \(\text{HCHO}(g)\), is shown:

\[ \text{HCHO}(g) + \text{O}_2(g) \rightarrow \text{CO}_2(g) + \text{H}_2\text{O}(g) \quad \Delta H_{\text{reaction}} = -482\text{ kJ mol}^{-1} \]

Some average bond energy data is given in the table below.

| Bond | Bond Energy / \(\text{kJ mol}^{-1}\) |
|---|---|
| \(\text{C}-\text{H}\) | 410 |
| \(\text{O}=\text{O}\) | 496 |
| \(\text{C}=\text{O}\) (in \(\text{CO}_2\)) | 805 |
| \(\text{O}-\text{H}\) | 462 |

What is the bond energy of the \(\text{C}=\text{O}\) bond in methanal?

An organic compound, \(W\), contains only carbon, hydrogen, and oxygen. Complete combustion of a \(1.80\text{ g}\) sample of \(W\) in excess oxygen yields \(2.64\text{ g}\) of carbon dioxide, \(\text{CO}_2\), and \(1.08\text{ g}\) of water, \(\text{H}_2\text{O}\).

What is the empirical formula of \(W\)?

(Relative atomic masses, \(A_r\): \(\text{C} = 12.0\); \(\text{H} = 1.0\); \(\text{O} = 16.0\))

Which statement correctly describes and explains a trend in physical properties of Period 3 elements from sodium to chlorine?

Ethyl ethanoate is synthesised by reacting ethanoic acid and ethanol in the presence of an acid catalyst:

\[ \text{CH}_3\text{COOH}(l) + \text{C}_2\text{H}_5\text{OH}(l) \rightleftharpoons \text{CH}_3\text{COOC}_2\text{H}_5(l) + \text{H}_2\text{O}(l) \]

In an experiment, \(1.00\text{ mol}\) of ethanoic acid and \(1.00\text{ mol}\) of ethanol are mixed and allowed to reach equilibrium at a constant temperature. At equilibrium, \(0.67\text{ mol}\) of ethyl ethanoate is present.

What is the value of the equilibrium constant, \(K_c\), at this temperature?

The standard enthalpy changes of combustion of carbon, hydrogen, and liquid propanone, \(C_3H_6O(l)\), are given below: \(\Delta H^\ominus_c [C(s)] = -393.5\text{ kJ mol}^{-1}\), \(\Delta H^\ominus_c [H_2(g)] = -285.8\text{ kJ mol}^{-1}\), \(\Delta H^\ominus_c [C_3H_6O(l)] = -1790.0\text{ kJ mol}^{-1}\). What is the standard enthalpy change of formation, \(\Delta H^\ominus_f\), of liquid propanone?

A sample of 2.102 g of a metal carbonate, \(MCO_3\), reacts completely with excess dilute hydrochloric acid to produce 504 cm\(^3\) of carbon dioxide gas measured at room temperature and pressure (r.t.p.). What is the relative atomic mass, \(A_r\), of the metal \(M\)? (Assume 1 mole of gas occupies 24.0 dm\(^3\) at r.t.p.)

An element, \(X\), in Period 3 of the Periodic Table forms a chloride which is a liquid at room temperature and pressure. This chloride reacts violently with water to form a strongly acidic solution and white fumes. The oxide of \(X\) has a giant covalent structure and is insoluble in water, but reacts with hot concentrated aqueous sodium hydroxide. What is element \(X\)?

Consider the following dynamic equilibrium: \(2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g)\) \(\Delta H = -197\text{ kJ mol}^{-1}\). What happens to the position of equilibrium and the value of the equilibrium constant, \(K_c\), when the temperature is increased at constant pressure?

In a calorimeter, 50.0 cm\(^3\) of 2.00 mol dm\(^{-3}\) \(NaOH(aq)\) is mixed with 50.0 cm\(^3\) of 2.00 mol dm\(^{-3}\) \(HNO_3(aq)\). Both solutions are initially at 21.5 \(^\circ\)C. The temperature rises to a maximum of 35.1 \(^\circ\)C. Assume the density of the mixture is 1.00 g cm\(^{-3}\) and its specific heat capacity is 4.18 J g\(^{-1}\) K\(^{-1}\). What is the enthalpy change of neutralization, \(\Delta H_{neut}\), for this reaction?

A sample of 10 cm\(^3\) of a gaseous hydrocarbon, \(Y\), is exploded with 100 cm\(^3\) of oxygen (an excess). After cooling to room temperature, the remaining gas mixture has a volume of 75 cm\(^3\). When this gas mixture is passed through aqueous potassium hydroxide (which absorbs \(CO_2\)), the volume decreases to 35 cm\(^3\). All gas volumes are measured at the same temperature and pressure. What is the molecular formula of \(Y\)?

Three Period 3 elements, \(X\), \(Y\), and \(Z\), have the following properties: Element \(X\) conducts electricity in both solid and liquid states and has a high melting point. Element \(Y\) has a giant covalent structure and does not conduct electricity under standard conditions. Element \(Z\) exists as diatomic molecules at room temperature. What are elements \(X\), \(Y\), and \(Z\)?

For the reversible reaction \(N_2O_4(g) \rightleftharpoons 2NO_2(g)\), a mixture at equilibrium at a temperature \(T\) has a total pressure of 1.20 atm. The partial pressure of \(N_2O_4(g)\) is 0.40 atm. What is the value of the equilibrium constant \(K_p\) at this temperature?

A \(1.48\text{ g}\) sample of an anhydrous metal carbonate, \(\text{MCO}_3\), is reacted completely with excess dilute hydrochloric acid. The volume of carbon dioxide gas collected at room temperature and pressure (r.t.p.) is \(240\text{ cm}^3\). What is the identity of metal M? [1 mol of gas occupies \(24.0\text{ dm}^3\) at r.t.p.]

A \(25.0\text{ cm}^3\) sample of a solution containing iron(II) ions, \(\text{Fe}^{2+}\), is titrated against acidified potassium manganate(VII), \(\text{KMnO}_4\). The titration requires \(18.5\text{ cm}^3\) of \(0.0200\text{ mol dm}^{-3}\) \(\text{KMnO}_4\) for complete oxidation of the \(\text{Fe}^{2+}\) ions. What is the concentration of \(\text{Fe}^{2+}\) in the solution?

Gaseous hydrazine, \(\text{N}_2\text{H}_4(\text{g})\), combusts in oxygen to form nitrogen gas and steam according to the equation:
\(\text{N}_2\text{H}_4(\text{g}) + \text{O}_2(\text{g}) \rightarrow \text{N}_2(\text{g}) + 2\text{H}_2\text{O}(\text{g})\)
Using the bond energies provided, what is the standard enthalpy change of this combustion reaction?

- \(\text{N}-\text{H}\): \(391\text{ kJ mol}^{-1}\)
- \(\text{N}-\text{N}\): \(158\text{ kJ mol}^{-1}\)
- \(\text{O}=\text{O}\): \(496\text{ kJ mol}^{-1}\)
- \(\text{N}\equiv\text{N}\): \(945\text{ kJ mol}^{-1}\)
- \(\text{O}-\text{H}\): \(463\text{ kJ mol}^{-1}\)

The standard enthalpy changes of formation for three substances are given below:
- \(\Delta H_f^\theta [\text{CO}_2(\text{g})] = -393.5\text{ kJ mol}^{-1}\)
- \(\Delta H_f^\theta [\text{H}_2\text{O}(\text{l})] = -285.8\text{ kJ mol}^{-1}\)
- \(\Delta H_f^\theta [\text{C}_3\text{H}_8(\text{g})] = -104.6\text{ kJ mol}^{-1}\)

What is the standard enthalpy change of combustion of propane, \(\text{C}_3\text{H}_8(\text{g})\)?

Four Period 3 elements, W, X, Y, and Z, form oxides with the properties described below:
- The oxide of W is a gas at room temperature and dissolves in water to form a strongly acidic solution.
- The oxide of X has a giant covalent structure and is insoluble in water.
- The oxide of Y is ionic and amphoteric.
- The oxide of Z reacts violently with water to form a strongly alkaline solution.

Which sequence correctly identifies the elements W, X, Y, and Z in order of increasing atomic number?

The first six successive ionisation energies (in \(\text{kJ mol}^{-1}\)) for an element, Q, in Period 3 of the Periodic Table are shown below:

- 1st: 578
- 2nd: 1817
- 3rd: 2745
- 4th: 11578
- 5th: 14831
- 6th: 18378

Which statement about element Q is correct?

The following gaseous equilibrium is established in a closed container of fixed volume:
\(2\text{NO}_2(\text{g}) \rightleftharpoons \text{N}_2\text{O}_4(\text{g}) \quad \Delta H = -58\text{ kJ mol}^{-1}\)

If the temperature of the container is increased, what happens to the value of the equilibrium constant, \(K_c\), and the total pressure inside the container?

Ethanol and ethanoic acid react to form ethyl ethanoate and water in a reversible reaction:
\(\text{CH}_3\text{COOH}(\text{l}) + \text{CH}_3\text{CH}_2\text{OH}(\text{l}) \rightleftharpoons \text{CH}_3\text{COOCH}_2\text{CH}_3(\text{l}) + \text{H}_2\text{O}(\text{l})\)

A mixture containing \(1.00\text{ mol}\) of ethanoic acid and \(1.00\text{ mol}\) of ethanol is allowed to reach equilibrium at a constant temperature. At equilibrium, \(0.67\text{ mol}\) of ethyl ethanoate is found to have formed. What is the value of the equilibrium constant, \(K_c\), at this temperature?

A 5.00 g sample of a dry mixture containing anhydrous magnesium nitrate, \( \text{Mg(NO}_3)_2 \), and magnesium oxide, \( \text{MgO} \), is heated strongly until no further decomposition occurs. Under these conditions, only the magnesium nitrate decomposes, producing \( 1.20 \text{ dm}^3 \) of gaseous product measured at room temperature and pressure (r.t.p.). What is the percentage by mass of magnesium nitrate in the original mixture? [Molar volume of gas at r.t.p. = \( 24.0 \text{ dm}^3 \text{ mol}^{-1} \); \( M_r: \text{Mg(NO}_3)_2 = 148.3 \)]

A 1.89 g sample of hydrated oxalic acid, \( \text{H}_2\text{C}_2\text{O}_4 \cdot x\text{H}_2\text{O} \), was dissolved in distilled water and made up to a total volume of \( 250 \text{ cm}^3 \). A \( 25.0 \text{ cm}^3 \) portion of this solution required exactly \( 25.00 \text{ cm}^3 \) of \( 0.120 \text{ mol dm}^{-3} \) sodium hydroxide, \( \text{NaOH} \), for complete neutralisation. What is the value of \( x \)? [\( M_r: \text{H}_2\text{C}_2\text{O}_4 = 90.0 \); \( M_r: \text{H}_2\text{O} = 18.0 \)]

The standard enthalpy changes of combustion of carbon, hydrogen, and liquid pent-1-yne, \( \text{C}_5\text{H}_8(l) \), are given in the table below.

\( \Delta H^\theta_c [\text{C}(s)] = -393.5 \text{ kJ mol}^{-1} \)
\( \Delta H^\theta_c [\text{H}_2(g)] = -285.8 \text{ kJ mol}^{-1} \)
\( \Delta H^\theta_c [\text{C}_5\text{H}_8(l)] = -3204.0 \text{ kJ mol}^{-1} \)

What is the standard enthalpy change of formation of liquid pent-1-yne?

The table below lists some average bond energies.

\( \text{C–H} = 413 \text{ kJ mol}^{-1} \)
\( \text{F–F} = 158 \text{ kJ mol}^{-1} \)
\( \text{C–F} = 467 \text{ kJ mol}^{-1} \)
\( \text{H–F} = 562 \text{ kJ mol}^{-1} \)

What is the enthalpy change for the gas-phase reaction shown below?
\( \text{CH}_4(g) + 2\text{F}_2(g) \rightarrow \text{CH}_2\text{F}_2(g) + 2\text{HF}(g) \)

Two Period 3 elements, P and Q, react with oxygen under appropriate conditions to form oxides. When these oxides are separately added to excess distilled water, the oxide of P forms a solution with a pH of approximately 13, while the oxide of Q forms a solution with a pH of approximately 2. What are elements P and Q?

Which of the following lists contains four Period 3 ions arranged in order of increasing ionic radius?

Initially, 2.0 mol of gaseous A and 3.0 mol of gaseous B are mixed in a sealed vessel of volume \( 2.0 \text{ dm}^3 \). The system is allowed to reach equilibrium at a constant temperature according to the equation:

\( \text{A}(g) + 2\text{B}(g) \rightleftharpoons 2\text{C}(g) \)

At equilibrium, the vessel is found to contain 1.2 mol of C. What is the value of the equilibrium constant, \( K_c \), at this temperature?

Consider the following exothermic reversible reaction at equilibrium in a closed system:

\( 2\text{SO}_2(g) + \text{O}_2(g) \rightleftharpoons 2\text{SO}_3(g) \quad \Delta H = -197 \text{ kJ mol}^{-1} \)

Which of the following changes will increase both the equilibrium yield of \( \text{SO}_3(g) \) and the value of the equilibrium constant, \( K_c \)?

An anhydrous mixture containing sodium carbonate, \( \text{Na}_2\text{CO}_3 \), and sodium hydrogencarbonate, \( \text{NaHCO}_3 \), has a total mass of \( 2.50\text{ g} \). This mixture is heated until no further reaction occurs.

The thermal decomposition of sodium hydrogencarbonate produces sodium carbonate, carbon dioxide, and water vapor as shown below:
\[ 2\text{NaHCO}_3(\text{s}) \rightarrow \text{Na}_2\text{CO}_3(\text{s}) + \text{CO}_2(\text{g}) + \text{H}_2\text{O}(\text{g}) \]

(a) (i) Explain why sodium carbonate does not decompose under the same conditions. [1]
(ii) Suggest why the solid residue after heating has a lower mass than the original mixture. [1]

(b) The gaseous products, \( \text{CO}_2 \) and \( \text{H}_2\text{O} \), are collected. After removing the water vapor, the volume of dry carbon dioxide gas collected is found to be \( 180\text{ cm}^3 \) measured at \( 298\text{ K} \) and \( 101\text{ kPa} \).

(i) Calculate the amount, in moles, of carbon dioxide gas collected. Treat carbon dioxide as an ideal gas. [2]
(ii) Hence, calculate the mass of \( \text{NaHCO}_3 \) present in the original \( 2.50\text{ g} \) mixture. [2]
(iii) Calculate the percentage by mass of \( \text{Na}_2\text{CO}_3 \) in the original mixture. [2]

(c) In a separate experiment, a \( 1.45\text{ g} \) sample of hydrated sodium carbonate, \( \text{Na}_2\text{CO}_3 \cdot x\text{H}_2\text{O} \), is dissolved in water to make \( 250.0\text{ cm}^3 \) of solution. A \( 25.0\text{ cm}^3 \) portion of this solution requires \( 20.25\text{ cm}^3 \) of \( 0.0500\text{ mol dm}^{-3} \) hydrochloric acid for complete neutralisation.
\[ \text{Na}_2\text{CO}_3 + 2\text{HCl} \rightarrow 2\text{NaCl} + \text{CO}_2 + \text{H}_2\text{O} \]

(i) Calculate the amount, in moles, of \( \text{HCl} \) used in the titration. [1]
(ii) Calculate the amount, in moles, of sodium carbonate present in the entire \( 250.0\text{ cm}^3 \) flask. [2]
(iii) Determine the value of \( x \) in \( \text{Na}_2\text{CO}_3 \cdot x\text{H}_2\text{O} \). [1]

A student carries out an experiment to determine the enthalpy change of combustion, \( \Delta H_c \), of liquid propan-1-ol, \( \text{C}_3\text{H}_7\text{OH} \).

A sample of propan-1-ol is burned in a spirit burner to heat \( 150\text{ g} \) of water in a copper calorimeter. The following results are obtained:
- Mass of spirit burner before combustion = 124.85 g
- Mass of spirit burner after combustion = 124.35 g
- Temperature of water before heating = \( 21.5^\circ\text{C} \)
- Temperature of water after heating = \( 43.5^\circ\text{C} \)
- Specific heat capacity of water, \( c = 4.18\text{ J g}^{-1}\text{ K}^{-1} \)

(a) (i) Calculate the heat energy, in kJ, absorbed by the water. [1]
(ii) Calculate the amount, in moles, of propan-1-ol burned. [2]
(iii) Calculate the experimental enthalpy change of combustion, \( \Delta H_c \), of propan-1-ol. Include a sign and appropriate units. [2]

(b) Suggest two reasons why the experimental value of \( \Delta H_c \) calculated in (a)(iii) is much less exothermic than the standard data book value of \( -2021\text{ kJ mol}^{-1} \). [2]

(c) The theoretical standard enthalpy change of combustion of propan-1-ol can be calculated using standard enthalpy changes of formation, \( \Delta H^\theta_f \):
- \( \Delta H^\theta_f [\text{C}_3\text{H}_7\text{OH(l)}] = -303\text{ kJ mol}^{-1} \)
- \( \Delta H^\theta_f [\text{CO}_2\text{(g)}] = -394\text{ kJ mol}^{-1} \)
- \( \Delta H^\theta_f [\text{H}_2\text{O(l)}] = -286\text{ kJ mol}^{-1} \)

(i) Write the balanced chemical equation, including state symbols, for the complete combustion of propan-1-ol. [1]
(ii) Calculate the theoretical standard enthalpy change of combustion, \( \Delta H^\theta_c \), of propan-1-ol using the provided \( \Delta H^\theta_f \) values. [2]

(d) Define the term *standard enthalpy change of formation*. [2]

The elements in Period 3 show characteristic trends in their physical and chemical properties.

(a) Phosphorus and sulfur form the oxides \( \text{P}_4\text{O}_{10} \) and \( \text{SO}_3 \) respectively.

(i) State the structure and bonding of phosphorus(V) oxide, \( \text{P}_4\text{O}_{10} \), and sulfur trioxide, \( \text{SO}_3 \). [2]
(ii) Write equations for the separate reactions of \( \text{P}_4\text{O}_{10} \) and \( \text{SO}_3 \) with water, and state the approximate pH of each resulting solution. [4]

(b) Silicon tetrachloride, \( \text{SiCl}_4 \), and sodium chloride, \( \text{NaCl} \), behave differently when added to water.

(i) Write the equation for the reaction of \( \text{SiCl}_4 \) with water, and state the approximate pH of the solution. [2]
(ii) Explain, in terms of structure and the availability of orbitals, why \( \text{SiCl}_4 \) reacts vigorously with water whereas \( \text{NaCl} \) simply dissolves to form a neutral solution. [2]

(c) Aluminium oxide, \( \text{Al}_2\text{O}_3 \), is amphoteric.

Write two ionic equations to demonstrate the amphoteric behavior of aluminium oxide. [2]

Methanol is produced industrially by the reversible reaction of carbon monoxide with hydrogen in the presence of a catalyst:

\[ \text{CO(g)} + 2\text{H}_2\text{(g)} \rightleftharpoons \text{CH}_3\text{OH(g)} \]

The forward reaction is exothermic with \( \Delta H = -91\text{ kJ mol}^{-1} \).

(a) Write the expression for the equilibrium constant, \( K_c \), for this reaction, and state its units. [2]

(b) A mixture of \( 1.20\text{ mol} \) of \( \text{CO} \) and \( 2.40\text{ mol} \) of \( \text{H}_2 \) is sealed in a \( 5.00\text{ dm}^3 \) flask at a constant temperature of \( 500\text{ K} \). When equilibrium is reached, \( 0.40\text{ mol} \) of \( \text{CH}_3\text{OH} \) has been formed.

(i) Calculate the equilibrium amounts, in moles, of \( \text{CO} \) and \( \text{H}_2 \). [2]
(ii) Calculate the value of \( K_c \) at \( 500\text{ K} \). [3]

(c) The temperature of the flask is now increased to \( 600\text{ K} \) while keeping the volume constant.

(i) State and explain the effect of this temperature increase on the value of \( K_c \). [2]
(ii) State and explain the effect of this temperature increase on the rate of the forward reaction. [2]

(d) Explain why the addition of a catalyst does not change the position of the equilibrium. [1]

Halogenoalkanes are important intermediates in organic synthesis. Two structural isomers with the molecular formula \( \text{C}_4\text{H}_9\text{Br} \) are:
- Isomer A: 1-bromobutane, \( \text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{Br} \)
- Isomer B: 2-bromo-2-methylpropane, \( (\text{CH}_3)_3\text{CBr} \)

(a) (i) Classify Isomer A and Isomer B as primary, secondary, or tertiary halogenoalkanes. [2]
(ii) Describe the mechanism for the reaction of Isomer B with aqueous sodium hydroxide, \( \text{NaOH(aq)} \). Use curly arrows to show the movement of electron pairs, and include any relevant partial charges, lone pairs, and intermediates. [4]

(b) The relative rate of hydrolysis of these halogenoalkanes can be investigated by heating each isomer separately with aqueous silver nitrate in ethanol.

(i) State the colour of the precipitate observed when the halogenoalkanes react. [1]
(ii) Explain which isomer, A or B, reacts faster in this reaction. Refer to the mechanism of the reaction in your answer. [2]

(c) Under different conditions, Isomer A can undergo an elimination reaction to form an alkene.

(i) Identify a suitable reagent and solvent for this elimination reaction. [2]
(ii) State the IUPAC name of the organic product formed from this elimination reaction of Isomer A. [1]

### Determination of the percentage by mass of sodium carbonate in a mixture

You are to determine the percentage by mass of sodium carbonate, \(\text{Na}_2\text{CO}_3\), in a solid mixture of sodium carbonate and sodium chloride, **FA 1**.
You will prepare a solution of the mixture and titrate it against a standard solution of hydrochloric acid, **FA 2**, of concentration \(0.115\text{ mol dm}^{-3}\).

The equation for the reaction is:
\[\text{Na}_2\text{CO}_3(\text{aq}) + 2\text{HCl}(\text{aq}) \rightarrow 2\text{NaCl}(\text{aq}) + \text{CO}_2(\text{g}) + \text{H}_2\text{O}(\text{l})\]

#### Procedure
1. Weigh a clean, dry weighing bottle.
2. Add between 2.20 g and 2.60 g of **FA 1** to the bottle and record the mass.
3. Transfer the solid to a beaker, reweigh the empty weighing bottle, and calculate the mass of **FA 1** transferred.
4. Dissolve the solid in about 100 cm3 of distilled water, transfer the solution quantitatively to a 250 cm3 volumetric flask, make up to the mark with distilled water, and mix thoroughly. Label this solution **FA 3**.
5. Pipette 25.0 cm3 of **FA 3** into a conical flask. Add 3–4 drops of methyl orange indicator.
6. Titrate **FA 3** with the standard hydrochloric acid, **FA 2**, contained in a burette.
7. Record your titration results in a suitable table in the space below. Repeat the titration until you obtain concordant results (within \(0.10\text{ cm}^3\)).

#### Questions
**(a)** Present your titration results in a clear table, including all raw burette readings and volumes of **FA 2** added. (4.00 marks)

**(b)** Show which results you used to calculate the average titre and write down this value. (1.33 marks)

**(c)** Calculate:
- (i) the number of moles of \(\text{HCl}\) in the average titre volume of **FA 2**.
- (ii) the number of moles of \(\text{Na}_2\text{CO}_3\) in 25.0 cm3 of **FA 3**.
- (iii) the number of moles of \(\text{Na}_2\text{CO}_3\) in the 250.0 cm3 volumetric flask.
- (iv) the percentage by mass of \(\text{Na}_2\text{CO}_3\) in the original solid mixture **FA 1**. (6.00 marks)

**(d)** Calculate the percentage error in the volume of **FA 2** delivered from a Class B burette (uncertainty of \(\pm0.05\text{ cm}^3\) for each reading) for your average titre. Suggest one modification to the experimental procedure (without changing the apparatus or reactants) that would reduce the percentage error in the titration volume. (2.00 marks)

### Enthalpy change of hydration of anhydrous copper(II) sulfate

You will determine the enthalpy change of solution of anhydrous copper(II) sulfate and hydrated copper(II) sulfate, and then use Hess's Law to calculate the enthalpy change of hydration of anhydrous copper(II) sulfate.

**FA 4** is anhydrous copper(II) sulfate, \(\text{CuSO}_4\).
**FA 5** is hydrated copper(II) sulfate, \(\text{CuSO}_4\cdot5\text{H}_2\text{O}\).

#### Procedure

##### Experiment 1: Enthalpy change of solution of anhydrous copper(II) sulfate
1. Support a plastic cup in a 250 cm3 beaker.
2. Use a measuring cylinder to transfer 50.0 cm3 of distilled water into the plastic cup.
3. Measure and record the initial temperature of the water to the nearest \(0.2\ ^\circ\text{C}\).
4. Weigh a weighing bottle containing between 3.80 g and 4.20 g of anhydrous copper(II) sulfate, **FA 4**. Record the mass.
5. Add the **FA 4** to the water in the plastic cup, stir continuously, and record the maximum temperature achieved.
6. Reweigh the weighing bottle to determine the mass of **FA 4** transferred.

##### Experiment 2: Enthalpy change of solution of hydrated copper(II) sulfate
1. Empty and dry the plastic cup.
2. Repeat the procedure using 50.0 cm3 of distilled water and between 5.80 g and 6.20 g of hydrated copper(II) sulfate, **FA 5**.
3. Record the initial temperature and the minimum temperature achieved.

#### Questions
**(a)** Present your results for both Experiment 1 and Experiment 2 in clear tables. Include all mass and temperature measurements with their appropriate units. (4.00 marks)

**(b)** Calculate:
- (i) the heat energy change, \(q_1\), for Experiment 1 (assume density of water = \(1.00\text{ g cm}^{-3}\) and specific heat capacity \(c = 4.18\text{ J g}^{-1}\ ^\circ\text{C}^{-1}\)).
- (ii) the enthalpy change of solution, \(\Delta H_1\), of anhydrous \(\text{CuSO}_4\) in \(\text{kJ mol}^{-1}\).
- (iii) the heat energy change, \(q_2\), for Experiment 2.
- (iv) the enthalpy change of solution, \(\Delta H_2\), of hydrated \(\text{CuSO}_4\cdot5\text{H}_2\text{O}\) in \(\text{kJ mol}^{-1}\). (5.33 marks)

**(c)** Draw a Hess's Law cycle showing how \(\Delta H_1\), \(\Delta H_2\), and the enthalpy change of hydration, \(\Delta H_{\text{hyd}}\), of anhydrous copper(II) sulfate are related. Use your cycle to calculate \(\Delta H_{\text{hyd}}\). (2.00 marks)

**(d)** State how heat loss to the surroundings would affect the calculated value of \(\Delta H_1\) (make it more negative or less negative) and suggest one improvement to the apparatus to reduce heat loss. (2.00 marks)

### Qualitative Analysis: Identification of unknown ions

You will carry out tests to identify the cations and anions present in three unknown aqueous solutions, **FA 6**, **FA 7**, and **FA 8**.

#### Procedure

Perform the following tests on each solution and record your observations in the spaces provided.

| Test | Instructions |
| :--- | :--- |
| **Test 1** | Add aqueous sodium hydroxide, \(\text{NaOH}(\text{aq})\), dropwise and then in excess to 1 cm3 of each solution in a test-tube. Warm the mixture with **FA 8** carefully, and test any gas evolved with damp red litmus paper. |
| **Test 2** | Add aqueous ammonia, \(\text{NH}_3(aq)\), dropwise and then in excess to 1 cm3 of each solution in a test-tube. |
| **Test 3** | Add 1 cm3 of aqueous barium chloride, \(\text{BaCl}_2(\text{aq})\) (or barium nitrate), to 1 cm3 of each solution, followed by dilute nitric acid. |
| **Test 4** | Add 1 cm3 of aqueous silver nitrate, \(\text{AgNO}_3(\text{aq})\), to 1 cm3 of each solution, followed by dilute aqueous ammonia. |

#### Questions
**(a)** Record your observations for **Test 1** and **Test 2** in a suitable table. (4.00 marks)

**(b)** Record your observations for **Test 3** and **Test 4** in a suitable table. (4.00 marks)

**(c)** Identify the cations and anions present in each solution. Support each identification with a brief explanation referencing your observations.
- **FA 6**: Cation = \_\_\_\_\_\_\_\_, Anion = \_\_\_\_\_\_\_\_
- **FA 7**: Cation = \_\_\_\_\_\_\_\_, Anion = \_\_\_\_\_\_\_\_
- **FA 8**: Cation = \_\_\_\_\_\_\_\_, Anion = \_\_\_\_\_\_\_\_ (3.33 marks)

**(d)** Write ionic equations for:
- (i) the formation of the precipitate when **FA 6** reacts with aqueous sodium hydroxide.
- (ii) the reaction that occurs when excess aqueous sodium hydroxide is added to **FA 7** and the precipitate dissolves. (2.00 marks)