Question

A student is studying a reaction between reactants A and B. the reaction is second order with respect to A, but zero order with respect to B. Explain in 5-6 sentences what this means.

If the Concetration of A is tripled what will the effect be on the reaction rate?

If the concentration of B is increased 10 times, what will the effect be on the reaction rate?

Answer 1

The rate of a reaction is defined as the rate of increase in the formation of the product in a reaction with time. For a reaction

A + B gives product

rate = k [A]^x [B]^y

given that x = 2 and y = 0

This means the rate of reaction depends only on the square of the concentration of A. Concentration of B doesn't have any influence on the rate of reaction. Even though B is participating in the reaction, it doesn't have any influence on the total rate of the reaction. At the same time, doubling the concentration of reactant A will quadruple the rate the reaction. Any change in concentration of B will not alter the reaction rate.

Given that

rate = k [A]² [B]⁰

suppose initial concentration of A = z

then

rate = z²

if we are tripling the concentration of A

ie [A] = 3z

rate = k [A]² [B]⁰

rate = 9z². the rate of reaction is increased by 9 times.

If the concentration of B is increased 10 times

the rate will not change

rate = k [A]² [B]⁰