Please provide answer and if possible explanation

Question

In the decomposition of ammonia on a platinum surface at 856 ^oC, 

2NH₃(g) → N₂(g) + 3H₂(g), changing the concentration of NH₃ has no effect on the rate. Which unit below is the correct unit for the rate constant in this case?

a. s^-1

b. mol^-1 L s^-1

c. mol L^-1 s^-1

d. mol^-3 L³ s^-1

e. mol² L^-2 s^-1

f. mol^-2 L² s^-1

Answer 1

The answer is C.

Having a reaction where changing the concentration of the reactant does not affect the rate is the textbook definition of a zero-order reaction. For zero-order reactions, the units are M/s, or mol L^-1s^-1.