Question

How to calculate unreacted concentration of A at 2hr when rate = k[A]¹[B]¹ (first order both A and B) and rate = k[A]⁰[B]⁰ (zero order both A and B) ?

A + B --> C, 1hr: A 75% reacted

Answer 1

A) Rate = k [A]¹[B]¹

              A     +         B      --> C

Initial     a               b             0

Final     a-x            b-x         x

dx / dt = rae of formation of C= K(a-x)(b-x)

dx/(a-x) (b-x) = Kdt

On integrating we will obtain

K = 1/ t(b-a) } lna(b-x) / ln b(a-x)

So if we know the rate constant and initial concentration we can find the value of x an hence the unreacted concentration of A

B) rate = k[A]⁰[B]⁰

so dx/ dt = K[A]⁰[B]⁰

or dx = dt

On integrating we will have

K =x/t

So if we know the value of K we can calculate the value of x at time 2 hours