One of the steps in the Ostwald process for the production of nitric acid involves oxidation of ammonia.

Question

4NH3 (aq) + 5O2 (g) <---> 4NO (g) + 6H2O (g), Delta H= -905kJ

a) State the reaction conditions that favour the production of nitrogen monoxide.
b) A rhodium/platinum alloy is used as a catalyst. What effect does the catalyst have on the position of the equilibrium. Explain.
c) A relatively low pressure of about 710 kPa is used. Suggest why.
d) In the next step of the Ostwald process, nitrogen monoxide is mixed with air to form nitrogen dioxide:

2NO (g) + O2(g) <----> 2NO2(g) , Delta H= -115kJ

Why are the gases cooled for this reaction?

Thanks

Answer 1

a) State the reaction conditions that favour the production of nitrogen monoxide.
If this question is asking for the best production AT EQUILIBRIUM then cool and low pressure. Under these conditions; however, the reaction is too slow to be useful and generally, in real practice, higher T and higher P are used.

b) A rhodium/platinum alloy is used as a catalyst. What effect does the catalyst have on the position of the equilibrium. Explain.
A catalyst changes ONLY the rate of the reaction. It has no effect on the final equilibrium.

c) A relatively low pressure of about 710 kPa is used. Suggest why.
Low pressure shifts the reaction to the side with fewer moles. That is the product side

d) In the next step of the Ostwald process, nitrogen monoxide is mixed with air to form nitrogen dioxide:

2NO (g) + O2(g) <----> 2NO2(g) , Delta H= -115kJ

Why are the gases cooled for this reaction?
<b.Cooling uses up the heat produced and shifts the reaction to the right.