Define activation energy as the minimum energy for a successful collision, sketch Maxwell-Boltzmann energy distribution curves at two temperatures with correct axes and shape, and use the area beyond Ea to explain why rate rises steeply with temperature.
Tę umiejętność sprawdza 26 zadań wzorowanych na arkuszach IB z lat 2022–2026.
The oxidation of sulfur dioxide to sulfur trioxide is an equilibrium reaction. 2 SO2(g) + O2(g) ⇌ 2 SO3(g) (i) State the equilibrium constant expression, K, for the reaction. (ii) Explain, with a reason, how compressing the gas mixture at constant…
Pentan-2-ol can form by reacting pent-1-ene with water in the presence of an acid catalyst. CH2=CHCH2CH2CH3(g) + H2O(l) → CH3CH(OH)CH2CH2CH3(aq) ΔH⊖ = −84 kJ mol−1 (i) Explain why increasing the temperature would increase…
Sodium reacts vigorously with water. (i) Write an equation, with state symbols, for the reaction of sodium with water. (ii) Describe one observation from the reaction in (i). (iii) Sketch, on the axes below, an energy profile for this reaction. Label the…
Propene can be reduced to propane by hydrogen gas in the presence of a platinum catalyst at 50 °C. Outline how the catalyst increases the rate of this reaction.
What is the effect of decreasing temperature on this Maxwell-Boltzmann energy distribution curve? A. The curve maximum is higher and to the left of A. B. The curve maximum is lower and to the right of A. C. The curve maximum is higher and to the right of A. D.…
Which statements describe the activation energy of a reaction? I. The minimum energy that colliding particles must have in order to react II. The energy difference between the reactants and the transition state on an energy profile III. The energy difference…
In moist air carbonyl dibromide is slowly hydrolyzed: Br2CO(g) + H2O(g) → CO2(g) + 2 HBr(g) (i) Suggest a method of monitoring the progress of this reaction at constant temperature so that its rate can be determined. (ii) Outline two reasons why a…
Increasing the temperature of a reaction mixture increases the rate of reaction. What is the best explanation for this? A. A greater proportion of collisions occur with energy greater than or equal to the activation energy. B. A greater proportion of…
The Maxwell–Boltzmann distribution below was obtained for a sample of gas at temperature T1. The activation energy of a reaction is marked as Ea. Which graph shows the distribution for the same sample at a higher temperature, T2, together…
(i) Sketch the Maxwell–Boltzmann energy distribution curve for the particles in this reaction mixture. Label the activation energy with and without the catalyst on the diagram. (ii) On the same axes, sketch and label a second Maxwell–Boltzmann curve for this…
(i) Sketch the Maxwell–Boltzmann distribution curve for 298 K on the same axes as the 800 K curve. (ii) On the graph, annotate the position corresponding to the activation energy, Ea. (iii) With reference to the graph, explain why a lower…
Which reaction has the lowest activation energy? A. HBr(g) → H(g) + Br(g) B. 2 Cl(g) → Cl2(g) C. CH4(g) + Cl(g) → CH3(g) + HCl(g) D. HBr(g) → H+(g) + Br−(g)
The diagram shows the energy profile of a reaction. P, Q and R are energies measured from the baseline of the potential energy axis. Which combination gives the activation energy of the forward reaction and the activation energy of the reverse reaction? A.…
Explain why a higher temperature speeds up this reaction, with the help of annotations that you add to the Maxwell-Boltzmann distribution below, which is drawn for a temperature T1.
Propenal can be made by the dehydration of propane-1,2,3-triol (glycerol): CH2(OH)CH(OH)CH2OH(l) → CH2=CHCHO(g) + 2 H2O(g) Two related reactions were studied separately. Reaction 1:…
Two gases react very slowly even at 900 K and a high pressure. Which best explains the low rate of reaction? A. The frequency of collisions between the molecules is low B. A high fraction of the collisions has the correct orientation C. The reaction is…
Sulfuryl chloride, SO2Cl2, is made industrially from sulfur dioxide and chlorine in the presence of an activated carbon catalyst. SO2(g) + Cl2(g) ⇌ SO2Cl2(g) ΔH⊖ < 0 (i) Sketch a potential energy profile for the forward reaction,…
Two samples of the same gas, at temperatures T1 and T2 where T2 > T1, have the Maxwell–Boltzmann distributions of kinetic energy shown. Which diagram is correct? A. Diagram A B. Diagram B C. Diagram C D. Diagram D
Sulfur trioxide is manufactured industrially by the oxidation of sulfur dioxide. 2 SO2(g) + O2(g) ⇌ 2 SO3(g) ΔH⊖ = −198.0 kJ mol−1 (i) Outline what is meant by dynamic equilibrium. (ii) Deduce the Kc expression for this…
Explain how a catalyst such as manganese(IV) oxide increases the rate of this reaction.
The solid curve in the enthalpy profile below is for a reaction carried out under one set of conditions. The dashed curve is obtained when the same reaction is carried out with one change. Which change is represented by the dashed curve? A. A higher…
The diagram shows the enthalpy profile of an exothermic reaction. Arrows I, II and III show energy differences on the profile. Which expression gives ΔH for the forward reaction? A. II − I B. I − II C. I + II D. III − II
Which expression gives the enthalpy change, ΔH, of the forward reaction shown in the enthalpy profile? A. II − I B. I − II C. I − III D. III − II
How does a catalyst increase the rate of a reaction? A. It increases the average kinetic energy of the colliding particles. B. It lowers the activation energy so that a greater proportion of collisions are successful. C. It makes the reaction more exothermic.…
(i) On the axes below, sketch Maxwell–Boltzmann energy distribution curves for the methanol molecules at two temperatures, T1 and T2, where T2 > T1. (ii) Explain the effect of increasing the temperature on the equilibrium yield of methanal.
A reaction has an activation energy of 50 kJ mol−1 and an enthalpy change of −70 kJ mol−1. Which potential energy diagram represents this reaction? A. Graph A B. Graph B C. Graph C D. Graph D
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