Question

During the kinetic study of the reaction, 2A + B → C + D,
following results were obtained:
Run [A](mol L⁻¹) [ B ](mol L⁻¹) Initial rate of
formation of
D (mol L⁻¹min⁻¹)
I 0.1 0.1 6.0 × 10⁻³
II 0.3 0.2 7.2 × 10⁻²
III 0.3 0.4 2.88 × 10⁻¹
IV 0.4 0.1 2.40 × 10⁻²
Based on the above data which one of the following is correct?
(a) rate = k [A]² [B] (b) rate = k[A] [B]
(c) rate = k[A]²[B]² (d) rate = k[A] [B]²

Answer 1

Explanation:

(b) rate = k[A] [B]

is the correct answer

Answer 2

Based on the data given to us , we can conclude that the rate law of the following reaction is: rate = k.[A].[B]²

• In data (I) and (IV), the concentration of B is constant but the concentration of A is made four times due to which the rate also becomes four times of the initial rate. Hence, rate is directly proportional to concentration of A.
• In data (II) and (III), the concentration of A is constant but the concentration of B is made double due to which the rate becomes four times of the initial rate. Hence, rate is directly proportional to the square of the concentration of B.
• Therefore, the rate = k.[A].[B]²