Question

The rate constant for a first order reaction is 4.606 × 10^–3 s^–1 . The time required to reduce 2.0 g of the reactant to 0.2 g is : 

(1) 1000 s 

(2) 100 s

(3) 200 s 

(4) 500 s

Answer 1

(4) 500 s

k = 4.606 × 10^–3 s^–1

kt = 2.303log₁₀ 2/0.2

4.606 x 10^-3 x t = 2.303 x log10

t = 1000/2

= 500s