For the reaction: Ba(OH)2 (s) + 2 NH4Cl (s) → BaCl2 (s) + 2 H2O (l) + NH3 (g)

Question

If ammonia gas (NH3) is produced at the rate of 0.72 mol/s, what is the corresponding rate of
consumption of ammonium chloride?
ANS: NH4Cl is consumed at a rate of 1.4 mol/s, twice as quickly as NH3 is produced

im confused how they came to this solution. is it by rate=k(A)^a(B)^b ??

Answer 1

No, not that. The ammonia is coming from the ammonium chloride alone. The rate of one has to equal the negative rate of the other. However, there is an error in your balanced equation, here it is corrected, and it might reveal a secret to you.
Ba(OH)2 (s) + 2 NH4Cl (s) → BaCl2 (s) + 2 H2O (l) + 2NH3 (g)

So in fact, your balanced equation was wrong, as was the answer provided.

Answer 2

So considering stoichiometry does that mean that ammonium chloride is being produced at a equal (0.72 mol/s) rate as it is being consumed