Rate Law [ENDORSED]

[Curtis Tam 1J]

In the book, it simply writes the rate law as rate=k[A][B] for example. But what does the "rate" actually refer to? The reactants? Products? Both?

Also, are there going to be any cases where we see a coefficient in the rate law. For example, something like rate=2*k[A][B]. In the book, it includes a coefficient of 2 in one the rate laws for the elementary equation but doesn't do the same for the overall rate law equation. Thx!

[joycelee1A]

I believe that the rate law is in reference to the reactants. For the coefficients, I think it has to do with the way the rate is defined. Like coefficients matter in the equation where rate=(1/a)d[A]/d[t]. Besides this equation, I'm not too sure about the coefficients.

[Vasiliki G Dis1C]

The rate law will be referring to whatever you designate it as. For example, lets say you have the reaction 2NH3 -> N2+ 3H2. If we define the rate as the consumption of NH3, we might have rate=k[NH3]. If we want to describe rate with respect to the other components of the reaction, we use coefficients. The rate of production of N2 would be rate= (1/2)k[NH3] and the rate of production of H2 would be rate=(2/3)k[NH3]. However, if we wanted to define the rate as the rate of production of N2 and this was rate=k2[N2]^2, the rate of consumption of NH3 would be rate=2k2[N2]^2 and the rate of production of H2 would be rate=3k2[N2]^2. Hope this helps!