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Section A [40 marksl

Answer all the questions in this section.

1. (a) A 20 dm3 closed vessel containing 1.5 mole H2g?s, x mole N2 gas and 1.2 mole CO2

gas has a total pressure of 500 kPa at a temperature of 298 K.

(i) Calculate the value of x. [3 marks]

(ii) 1.5 mole of neon gas was added into the 20 dm3 vesset. Calculate the

partial pressure of the hldrogen gas. [1 mark]

(b) Hydrazine, NzHr is used as fuel for rocket .

(i) Write the electronic configuration of nitrogen atom. [1 mark]

(ii) Draw the dot -cross structure for hydrazine molecule. [1 mark]

(c) The boiling point of dimethyl ether(CHsOCHs) is lower than that of propanone

(cH3cocH3).(i) Give a reason for the difference in their boiling points. [2 marks]

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(iv) e.m.f. , Eo en for the reaction in (b)(iii). [1mark]

(b) The phase diagram of a substance W is shown below.

Pressure(atm)

Temperaturefc)

(i) State all the changes of phases of substance W at the following points as thetemperature increases.

P: . . . . . .

R: . . . . . .

T: . . . . . .

[2marks]

(ii) Base on the curve oY, compare the density of solid w and liquid w. [1mark]

Q:

S:

(iii) Describe the change in melting point when pressure is increased [1mark]

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Section A [ 40 marks ]

Answer all questions in this section.

1. (a) Draw and name the shape of these following molecules :

(i) BeCl2

Shape :

(ii) CO3

2-

Shape :

(iii) NH4

+

Shape :

(iv) SF6 Shape :

[ 4 marks ]

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SECTION A

Answer all question in this section

1. The reaction between hydrogen and iodine can be represented by the following equation:

H2(g) + I2(g) 2HI(g) H = +52 kJ mol–1

Kinetic data are available for both forward and reverse reactions. A series of experiments to investigate the kinetics of the forward reaction was carried out at a constant temperature. The results are shown in Figure 1.

Experiment Initial concentration of

H2 / mol dm–3

Initial concentration of

I2 / mol dm–3

Initial rate

/ mol dm–3 s–1

1 2.0 × 10–3 3.0 × 10–3 l.2 × 10–6

2 6.0 × 10–3 3.0 × 10–3 3.6 × 10–6

3 6.0 × 10–3 6.0 × 10–3 7.2 × 10–6

Figure 1

(a) Explain the meaning of each of the following terms:

(i) rate constant;

(1)

(iii) overall order of reaction.

(2)

2  

(b) (i) Use the results in Figure 1 to work out the order of the forward reaction with respect to both hydrogen and iodine, explaining your reasoning.

(3)

(ii) Write the rate equation for the reaction between hydrogen and iodine.

(1)

(iii) Calculate the value of the rate constant for the forward reaction and give its units.

(2)

(c) The experiment was repeated with the following initial concentrations for reactants:

[H2] = 4.0 × 10–3 mol dm–3 [I2] = 5.0 × 10–3 mol dm–3

Calculate the initial rate of the reaction.

(1)

(Total 10 marks)

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Section A [40 marks]

Answer all questions in this section.

1 (a) A container of volume 25 dm3 contains 0.50 mol of hydrogen gas, 0.10 mol of oxygen gas and an unknown amount of helium gas. The pressure of 1 mol of gas in the container at room temperature is 100kPa.

(i) If the total pressure in the container is 88 kPa, determine the number of moles of helium gas in the container.

[2 marks]

(ii) The mixture of gases in the container is then ignited. What is the number of moles

of each gas left in the container after the ignition?

[1 mark]

(iii) After ignition, the container is allowed to cool to room temperature. What is the partial pressure of helium gas in the container?

[1 mark]

(iv) If the vapour pressure of water in the container at room temperature is 2.4 kPa, what is the total pressure in the container?

[1 mark]

(v) Write a balanced equation for the reaction that has taken place.

[1 mark]

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(b) The diagram below shows four electronic transitions in the hydrogen atom.

(i) Which electronic transition emits electromagnetic radiation with the shortest wavelength?

[1 mark]

(ii) In which region of the electromagnetic spectrum are these lines formed? What is

the name of this line series in the emission spectrum of hydrogen?

[2 marks]

(iii) Determine the maximum number of lines that can be formed in this line emission spectrum involving the the energy levels n=2 to n=6

[1 mark]

 

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Section B [60 marks]

Answer any four questions in this section.

5 (a) The boiling points of three fluorides are as follows :

Fluoride Boiling point / 0C SiF4 -86 0C PF5 -75 0C SF6 -64 0C

(i) Explain in terms of structure and bonding why these compounds are all gases at room

temperature and pressure [2 marks]

(ii) Draw diagrams to show the shapes and bond angles of each of these compounds

SiF4, PF5, and SF6. [3 marks]

(iii)Both oxygen and sulphur are in the same group in the Periodic Table. State why

compound OF6 does not exist. [1 mark]

(iv) Xenon reacts with fluorine to form the compound XeF4. State whether the Xe—F

bond is polar or non-polar and hence explain the polarity of XeF4 molecule. [3 marks]

(b) Carbon monoxide, CO, nitrogen monoxide, NO and oxygen react together to produce nitrogen dioxide, NO2 as one of the product. Several experiments were carried out to determine the rate equation for the reaction. The results are shown in the table below.

Experiment [CO(g)]/

mol dm-3 [NO(g)]/ mol dm-3

[O2(g)]/ mol dm-3

Initial rate/ mol dm-3 s-1

1 1.00 x 10-3 1.00 x 10-3 1.00 x 10-1 4.40 x 10-4 2 2.00 x 10-3 1.00 x 10-3 1.00 x 10-1 4.40 x 10-4 3 2.00 x 10-3 3.00 x 10-3 1.00 x 10-1 3.96 x 10-3 4 5.00 x 10-3 1.00 x 10-3 3.00 x 10-1 1.32 x 10-3

(i) Write an equation for the reaction between CO, NO and O2.

[1 mark]

(ii) Determine the order of the reaction with respect to each of the reactants and hence the rate equation

[4 marks]

(iii) Determine the rate constant, k for the reaction. [2 marks]