At high pressure the following reaction is zero order. $2{\mathrm{NH}}_3\left(\mathrm{g}\right)\frac{1130\mathrm{K}}{\text{ Platinum catalyst }}{\mathrm{N}}_2\left(\mathrm{g}\right)+3{\mathrm{H}}_2\left(\mathrm{g}\right)$
Which of the following options are correct for this reaction?

Given, chemical reaction is $2{\mathrm{NH}}_3\left(\mathrm{g}\right)\frac{1130\mathrm{K}}{\text{ Platinum catalyst }}{\mathrm{N}}_2\left(\mathrm{g}\right)+3{\mathrm{H}}_2\left(\mathrm{g}\right)$
At very high pressure reaction become independent of concentration of ammonia, i.e. zero order reaction.
Hence, Rate $=\mathrm{k}{\left[{\mathrm{p}}_{{\mathrm{NH}}_3}\right]}^0\Rightarrow \text{ Rate }=\mathrm{k}$
(a) Rate of reaction = Rate constant
(c) Rate of decomposition of ammonia will remain constant until ammonia disappears completely.
(d) Since, formation of ammonia is a reversible process further increase in pressure will change the rate of reaction. According to Le-Chatelier principle increase in pressure will      favour in backward reaction.