Assignment:
Kn1 knowledge and understanding of chemical equilibrium and the effects of external constraints, enthalpy of reaction and effects of catalysts on rates of chemical reactions.
Ky3 communicate scientific information in writing short accounts relaying information to a particular audience (your tutor).
Ammonia reacts with oxygen in the presence of a platinum catalyst to give nitric oxide and water, according to the following gas phase equilibrium:
4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g) ?H = -906 kJ mol-1
(a) Write an appropriate equilibrium expression for the reaction. What would the units of the equilibrium constant K be if the concentrations of all the gases in the equilibrium expression were measured in mol dm-3? Show how you determined your units for K using your equation.
(b) Write a short account of around 250 words in total, with reference to Le Chatelier's principle, in which you explain the following:
(i) The effect on the equilibrium yield of nitric oxide of increasing the pressure.
(ii) The effect on the equilibrium yield of nitric oxide of increasing the temperature.
(iii) The effect on the rate of reaction of increasing the temperature.
Write your account using concise scientific language. For the purposes of
this exercise you should assume that your tutor is your target audience.
(c) Describe what a catalyst is and what effect the presence of a platinum catalyst has on the equilibrium yield and on the rate of reaction. (Three or four sentences).
Provide complete and step by step solution for the question and show calculations and use formulas.