[Maximum number: 3]

Combustion data can be used to calculate the empirical formula, molecular formula and relative molecular mass of many organic compounds. Combustion data cannot distinguish between different structural isomers.

(a)

P is a hydrocarbon, $\mathrm{C}_{x} \mathrm{H}_{y^{\prime}}$ . A gaseous sample of P occupied a volume of $25 \mathrm{~cm}^{3}$ at $37^{\circ} \mathrm{C}$ and 100 kPa .

The sample was completely burned in $200 \mathrm{~cm}^{3}$ of oxygen (an excess).
The final volume, measured under the same conditions as the gaseous sample (so that the water produced is liquid and its volume can be ignored), was $150 \mathrm{~cm}^{3}$ .

Treating the remaining gaseous mixture with concentrated alkali, to absorb carbon dioxide, decreased the volume to $50 \mathrm{~cm}^{3}$ .

The equation for the complete combustion of P can be represented as shown.

\mathrm{C}_{x} \mathrm{H}_{y}+\left(x+\frac{y}{4}\right) \mathrm{O}_{2} \rightarrow x \mathrm{CO}_{2}+\frac{y}{2} \mathrm{H}_{2} \mathrm{O}

[ 3 ]

(i)

Use the general gas equation to calculate the mass of P present in the original $25 \mathrm{~cm}^{3}$ gaseous sample, which was measured at $37^{\circ} \mathrm{C}$ and 100 kPa .

Give your answer to three significant figures.

[ 3 ]

[Maximum number: 1]

Which diagram shows the correct graph of V against p for a fixed mass of an ideal gas at constant temperature?

A

B

C

D

[Maximum number: 1]

The temperature of a sample of an inert gas is increased.
What effect does this have on the number of molecules with the most probable energy and on the number of molecules with high energy?

number of molecules with the most probable energy

number of molecules with high energy

decreases

increases

decreases

increases

[Maximum number: 1]

The molecules of a gas at a constant temperature, $T_{1}$ , have the distribution of molecular energies shown in the diagram.

When the temperature is increased to $T_{2}$ , the distribution of molecular energies changes.
Which diagram correctly shows this change?

A

B

C

D

[Maximum number: 3]

The Pauling electronegativity values of elements can be used to predict the chemical properties of compounds.

Use the information in Table 1.1 to answer the following questions.

Table 1.1

(a)

(i)

At $150^{\circ} \mathrm{C}$ and 103 kPa , all of the compounds listed in Table 1.2 are gases.

Under these conditions, 0.284 g of one of the compounds occupies a volume of $127 \mathrm{~cm}^{3}$ .
Use this information to calculate the $M_{\mathrm{r}}$ of the compound. Hence, identify the compound from those given in Table 1.2.

Show your working.
$M_{\mathrm{r}}=$ identity of compound =

[ 3 ]

[Maximum number: 2]

Hydrogen iodide, HI, is a colourless gas at room temperature.

(a)

HI(g) can also be formed by the reaction of $\mathrm{I}_{2}(\mathrm{~g})$ with hydrazine, $\mathrm{N}_{2} \mathrm{H}_{4}(\mathrm{~g})$ .

2 \mathrm{I}_{2}(\mathrm{~g})+\mathrm{N}_{2} \mathrm{H}_{4}(\mathrm{~g}) \rightarrow 4 \mathrm{HI}(\mathrm{~g})+\mathrm{N}_{2}(\mathrm{~g})

State the change in pressure that would occur when $2 \mathrm{~mol} \mathrm{I}_{2}(\mathrm{~g})$ fully reacts with $1 \mathrm{~mol} \mathrm{~N}_{2} \mathrm{H}_{4}(\mathrm{~g})$ in a sealed container at constant temperature. Explain your answer.

[ 2 ]

[Maximum number: 6]

The rate of chemical reactions is affected by changes in temperature and pressure.

(a)

The Boltzmann distribution assumes that the particles behave as an ideal gas.

[ 6 ]

(i)

State two assumptions of the kinetic theory as applied to an ideal gas.

1

2

[ 2 ]

(ii)

2.00 g of krypton gas, Kr(g), is placed in a sealed $5.00 \mathrm{dm}^{3}$ container at $120^{\circ} \mathrm{C}$ .

Calculate the pressure, in Pa , of Kr(g) in the container. Assume Kr(g) behaves as an ideal gas.

Show your working.
pressure =

[ 2 ]

(iii)

State and explain the conditions at which krypton behaves most like an ideal gas.

[ 2 ]

[Maximum number: 3]

Combustion data can be used to calculate the empirical formula, molecular formula and relative molecular mass of many organic compounds.

(a)

T is an alcohol, $\mathrm{C}_{x} \mathrm{H}_{y} \mathrm{O}$ . A gaseous sample of T occupied a volume of $20 \mathrm{~cm}^{3}$ at $120^{\circ} \mathrm{C}$ and 100 kPa .

The sample was completely burned in $200 \mathrm{~cm}^{3}$ of oxygen (an excess). The final volume, measured under the same conditions as the gaseous sample, was $250 \mathrm{~cm}^{3}$ .

Under these conditions, all water present is vaporised. Removal of the water vapour from the gaseous mixture decreased the volume to $170 \mathrm{~cm}^{3}$ .

Treating the remaining gaseous mixture with concentrated alkali, to absorb carbon dioxide, decreased the volume to $110 \mathrm{~cm}^{3}$ .

The equation for the complete combustion of T can be represented as shown.

\mathrm{C}_{x} \mathrm{H}_{y} \mathrm{O}+z \mathrm{O}_{2} \rightarrow x \mathrm{CO}_{2}+\frac{y}{2} \mathrm{H}_{2} \mathrm{O}

[ 3 ]

(i)

Use the general gas equation to calculate the mass of T present in the original $20 \mathrm{~cm}^{3}$ gaseous sample, which was measured at $120^{\circ} \mathrm{C}$ and 100 kPa .

Give your answer to three significant figures. Show your working.

[ 3 ]

[Maximum number: 1]

Sulfides are compounds that contain sulfur but not oxygen.

(a)

Carbon disulfide, $\mathrm{CS}_{2}$ , is a volatile liquid at room temperature and pressure.

[ 1 ]

(i)

State the meaning of volatile.

[ 1 ]

[Maximum number: 2]

Aluminium is a metal in Period 3 and Group III of the Periodic Table.

(a)

Aluminium reacts with chlorine to form a white, solid chloride that contains 79.7 % chlorine and sublimes (changes straight from a solid to a gas) at $180^{\circ} \mathrm{C}$ .

[ 2 ]

(i)

Calculate the relative molecular mass, $M_{\mathrm{r}}$ , of the chloride. Give your answer to three significant figures.

M_{r}=

[ 2 ]

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