SL Equilibrium Question

[Cherries]

The reaction below represents the Haber process for the industrial production of ammonia.
    N2(g) + 3H2(g)   2NH3(g)    ∆HO = –92 kJ

The optimum conditions of temperature and pressure are chosen as a compromise between those that favour a high yield of ammonia and those that favour a fast rate of production. Economic considerations are also important.

Which statement is correct?
A.    A higher temperature would ensure higher yield and a faster rate.
B.    A lower pressure would ensure a higher yield at a lower cost.
C.    A lower temperature would ensure a higher yield and a faster rate.
D.    A higher pressure would ensure a higher yield at a higher cost.

The answer is D. I know that it is either C or D. I'm assuming it is D because only catalysts are responsible for increasing the rate but there is no such mention in this question. Is my reasoning correct?

Edited May 3, 2018 by Cherries

[kw0573]

A is wrong because at high temperature, equilibrium is shifted towards reactants by the Le Chatelier's Principle. C is wrong because at low temperature, rate is slow by the Maxwell-Boltzmann energy distribution.

At high pressure, equilibrium would shift to products, the side with less gaseous molecules. But because maintaining a high pressure is expensive, D is correct.