Question

 For a reaction, \[\ce{A + B -> C + D}\], the initial rate for different reactions and initial concentrations of reactants are given below:

S. No.	Initial Conc.		Initial rate (mole L–1 sec–1)
	[A] mole L–1	[B] mole L–1
1.	1.0	1.0	2 × 10−3
2.	2.0	1.0	4 × 10−3
3.	4.0	1.0	8 × 10−3
4.	1.0	2.0	2 × 10−3
5.	1.0	4.0	2 × 10−3

1. What is the overall order of reaction?
2. Write the rate law equation.

Answer 1

Given: r ∝ [A]^x [B]^y

i. Overall order of reaction:

Compare (ii)/(i):

`(4.0 xx 10^-3)/(2.0 xx 10^-3) = (2/1)^x`

⇒ 2 = 2x

⇒ x = 1.

Compare (iv)/(i):

`(2.0 xx 10^-3)/(2.0 xx 10^-3) = (1/1)^x (2/1)^y`

⇒ 1 = 2y

⇒ y = 0.

∴ Order in A = 1, Order in B = 0

Overall order = x + y 

= 1 + 0

= 1

ii. Rate law:

r = k [A]