Question

A reaction with stoichiometric equation 1/2A + B = R + 1/2S has the following rate expression –rA = 2CA 0.5 CB. What is the rate expression for this reaction if the stoichiometric equation is written as A + 2B = 2R + S?

Answer 1

Reaction equation: ½ A + B ====> R + ½ S

Rate of disappearance of A, -r_A = k[A]^0.5[B]

Can also be written as   -r_A = k C_A^0.5 C_B

rate expression given for the above reaction equation = -r_A = 2 C_A^0.5 C_B.

So the rate constant, k, of the reaction = 2

If the stoichiometric equation is written as A + 2B = 2R + S

Then the rate of disappearance of A will be, -r_A = k[A][B]²

Can also be written as   -r_A = k C_A C_B²

Since rate constant, k, of the reaction = 2

The rate of disappearance of A will be, -r_A = 2[A][B]²