Maxwell-Boltzmann distribution and catalystsEdexcel International A Level Chemistry: Mind map

Exam questions on Maxwell-Boltzmann distribution and catalysts

1. A chemist sketches Maxwell–Boltzmann distributions of molecular energies for the same sample of gas at 300 K and at 310 K. She notes that the mean kinetic energy of the molecules rises by only about 3% over this range, yet the rate of a reaction in the gas roughly doubles.
   Explain, using the Maxwell–Boltzmann distribution, why a rise in temperature of only 10 K can double the rate even though the mean kinetic energy rises very little.2 marks
2. Hydrogen peroxide solution decomposes slowly at room temperature to form water and oxygen. When a small amount of solid manganese(IV) oxide is added, oxygen is released rapidly, and the manganese(IV) oxide can be recovered unchanged at the end.
   Describe how the reaction profile for the catalysed route differs from the profile for the uncatalysed route, given that the catalyst forms an intermediate.2 marks
3. Ethanol can be made industrially by the catalysed hydration of ethene with steam, using phosphoric acid on a silica support at about 570 K. A laboratory alternative is to react bromoethane with aqueous sodium hydroxide, which gives sodium bromide as the only other product. A company wants to know which route is more sustainable.
   Explain, in terms of activation energy, how a catalyst allows a process to be carried out at a lower temperature, and why this makes the process more sustainable.3 marks