Consider the following reaction 2x --> y + z, when the concentration of x is doubled, the reaction rate increases by a factor of 4. what is the order of the reaction?

(a) zero order
(b) first-order
(c) second order
(d) third order

(C) second order

Explanation:

Let's consider the following reaction.

2X --> Y + Z

The rate law is:

r = k . [A]ˣ

where,

r is the rate of the reaction

k is the rate constant

x is the reaction order of A

Let's assume x = 2. If the concentration of A is doubled, the new rate r₁ is:

r₁ = k . [2A]² = 4 . k . [A]² = 4 . r

The new rate r₁ is 4 times r when [A] is doubled. This happens when x = 2, that is, it is a second reaction order.