6 questions · 8 marks · ≈ 8 min
What is the effect of increasing temperature on the average energy of the particles in a reaction and on the activation energy of the reaction?
| Effect on the average energy | Effect on the activation energy | ||
|---|---|---|---|
| ☐ | A | unchanged | decreased |
| ☐ | B | unchanged | unchanged |
| ☐ | C | increased | decreased |
| ☐ | D | increased | unchanged |
Choose your answer
The graph shows how the concentration of iodine changes with time in a reaction.
What is the value for the rate of reaction, in mol dm−3 s−1, at 8 seconds?
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0.01
0.02
0.03
0.25
The solid line on the graph below shows the Maxwell–Boltzmann distribution for an uncatalysed reaction. Ea is the activation energy of this reaction.
Which row shows the correct Maxwell–Boltzmann curve and activation energy for the reaction at a higher temperature with a catalyst?
| Maxwell-Boltzmann curve | Activation energy | ||
|---|---|---|---|
| ☐ | A | X | W |
| ☐ | B | X | Z |
| ☐ | C | Y | W |
| ☐ | D | Y | Z |
Choose your answer
Which conditions give the highest yield for the forward reaction?
NH4Cl (s) ⇌ NH3 (g) + HCl (g) Δ*H *= +176 kJ mol−1
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high temperature, high pressure
high temperature, low pressure
low temperature, high pressure
low temperature, low pressure
Nitrogen dioxide and dinitrogen tetroxide exist in equilibrium.
2NO2 (g) ⇌ N2O4 (g) brown gas colourless gas
When an equilibrium is set up in a gas syringe, the mixture is pale brown.
When the mixture is compressed the colour becomes
Choose your answer
darker
lighter
darker and then lighter
lighter and then darker
The Maxwell–Boltzmann distribution curves X and Y show the distribution of molecular kinetic energies for a fixed sample of gas under two different conditions.
Which change could be responsible for the difference between X and Y?
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Adding a catalyst
Increasing the concentration of reactant
Increasing the pressure
Increasing the temperature
Compared to condition X, what is the effect of condition Y on the rate of reaction?
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The rate decreases
The rate first increases then decreases
The rate increases
The rate stays the same
Which statement about the activation energy, Ea, is correct?
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Ea is the average energy of the reactant molecules
Ea is the difference in enthalpy between reactants and products
Ea is the minimum energy required for a successful collision
Ea is the total energy released by the reaction