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Question 1

In a spectrophotometric experiment, 84.9% of the incident light is absorbed by the solution under investigation. If the solution is of concentration 0.069 mol dm^-3, and the path length of the cell is 12.5 mm, calculate the molar absorption coefficient of the solution.

a) 2.24 mol^-1 dm^-3 cm^-1

b) 0.0824 mol^-1 dm^-3 cm^-1

c) 0.824 mol^-1 dm^-3 cm^-1

d) 1.21 mol^-1 dm^-3 cm^-1

Question 2

Which of the following statements about the kinetics of the reaction
H₂(g) + Br₂(g) → 2HBr (g) is definitely true?

a) The reaction is first order with respect to bromine, Br₂.

b) The reaction is second order overall.

c) The presence of hydrogen bromide, HBr, inhibits the rate of the reaction.

d) It is not possible to determine anything about the kinetics of the reaction from the stoichiometry.

Question 3

Which of the following would be correct units for the rate constant of a reaction that is second order overall?

a) s^-1

b) mol^-1 dm³s^-1

c) mol cm^-3 s^-1

d) mol^-2 dm⁶ s^-1

Question 4

The rate constant for the reaction
H₂ + OH → H + H₂O
which is an important step in the hydrogen-oxygen reaction mechanism, has the value k_r = 3.52 × 10⁶ mol^-1 dm³ s^-1. What is the equivalent value expressed in units of molecule^-1 cm³ s^-1?

a) 2.12 × 10²⁷ molecule^-1 cm³ s^-1

b) 5.85 × 10^-15 molecule^-1 cm³ s^-1

c) 5.85 × 10^-²¹ molecule^-1 cm³ s^-1

d) 2.12 × 10^-15 molecule^-1 cm³ s^-1

Question 5

In an experiment to investigate the mechanism of the condensation reaction between acrolein and 1,3-butadiene, the initial rate was measured spectrophotometrically for various different partial pressures of the reactants. The table below shows the initial rates of reaction, v₀, for various partial pressures of acrolein, p, at a temperature of 560 K with 1,3-butadiene being in excess.
Q.05 data
Use the method of initial rates to determine the order of the reaction with respect to acrolein.

a) 0

b) 1

c) 2

d) 3

Question 6

In an investigation of the first-order decomposition reaction
C₂H₅I → C₂H₄ + HI
at a temperature of 400K, the partial pressure of C₂H₅I, p, was found to vary with time, t, as shown below. Determine the rate constant of the reaction.
Q.06 data

a) 0.0259 s^-1

b) 38.6 s^-1

c) 0.175 s^-1

d) 0.455 s^-1

Question 7

The rate constant for the substitution reaction
C₄H₉Cl + H₂O → C₄H₉OH + HCl
increases by a factor of 10.6 when the temperature is increased from 298 K to 308 K. Calculate the activation energy of the reaction.

a) 180 kJ mol^-1

b) 78.2 kJ mol^-1

c) 809 kJ mol^-1

d) 2.14 kJ mol^-1

Question 8

The half life for the acid-catalysed hydrolysis of sucrose to form glucose and fructose, which is first order overall, is 3.20 h at 25°C. What is the rate constant for the reaction at this temperature?

a) 6.02 × 10^-5 s^-1

b) 8.68 × 10^-5 s^-1

c) 0.217 s^-1

d) 2.61 × 10^-5 s^-1

Question 9

The rate constant for the second order reaction between iodomethane, CH₃I, and ethoxy anions, C₂H₅O^-, in ethanol solution is 9.86 × 10^-5 mol dm^-3 s^-1 at 298 K and 6.17 × 10^-3 mol dm^-3 s^-1 at 338 K. Calculate the activation energy.

a) 300 kJ mol^-1

b) 116 kJ mol^-1

c) 10.4 kJ mol^-1

d) 86.6 kJ mol^-1

Question 10

Predict the Arrhenius pre-exponential factor for the reaction
H₂ + CO → H₂CO
at 298.15 K, given that the collision cross section of H₂ is 0.0452 nm² and of CO is 0.0804 nm^2.

a) 69.2 × 10⁶ mol^-1 m³ s^-1

b) 192 × 10⁶ mol^-1 m³ s^-1

c) 67.8 × 10⁶ mol^-1 m³ s^-1

d) 271× 10⁶ mol^-1 m³ s^-1

Oxford University Press, Online Resource Centre, Chapter 10.

Chapter 10

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