8.2. Effect of temperature on reaction rates and the concept of activation energy
A subsection of Chemistry, 9701, through 8. Reaction kinetics
Listing 10 of 111 questions
The diagram below shows, for a given temperature T, a Boltzmann distribution of the kinetic energy of the molecules of a mixture of two gases that will react together, such as nitrogen and hydrogen. The activation energy for the reaction, Ea, is marked. Ea energy number of molecules On the graph above, draw a new distribution curve, clearly labelled T, for the same mixture of gases at a higher temperature, T; mark clearly, as H, the position of the activation energy of the reaction at the higher temperature, T. Explain the meaning of the term activation energy. The reaction between nitrogen and hydrogen to produce ammonia in the Haber process is an example of a large-scale gaseous reaction that is catalysed. State the catalyst used and give the operating temperature and pressure of the Haber process. catalyst temperature pressure On the energy axis of the graph opposite, mark the position, clearly labelled C, of the activation energy of the reaction when a catalyst is used. Use your answer to to explain how the use of a catalyst results in reactions occurring at a faster rate. Two reactions involving aqueous NaOH are given below. CH3CHBrCH3 + NaOH CH3CH(OH)CH3 + NaBr reaction 1 HCl + NaOH NaCl + H2O reaction 2 In order for reaction 1 to occur, the reagents must be heated together for some time. On the other hand, reaction 2 is almost instantaneous at room temperature. Suggest brief explanations why the rates of these two reactions are very different. reaction 1 reaction 2
9701_s10_qp_21
THEORY
2010
Paper 2, Variant 1
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The diagram represents, for a given temperature, the Boltzmann distribution of the kinetic energies of the molecules in a mixture of two gases that will react together. The activation energy for the reaction, Ea , is marked. energy number of molecules Ea The dotted curves below show the Boltzmann distribution for the same reaction at a higher temperature. On these diagrams, H represents the activation energy at the higher temperature. Which diagram is correct?
9701_s13_qp_13
MCQ
2013
Paper 1, Variant 3
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Questions Discovered
111