Calculate the half-life of a first order reaction from their rate constants given below: (i) 200 s−1 (ii) 2 min−1 (iii) 4 years−1

Question 4.13: Calculate the half-life of a first order reaction from their rate constants given below:
(i) 200 s⁻¹ (ii) 2 min⁻¹ (iii) 4 years⁻¹
Answer
The formula of half life is t_1/2 = 0.693 / k … (1)
(i)
Given that k = 200 s^-1
plug the value of k in equation (1), we get
Half life, t _½ = 0.693/ 200 = 3.47 s (approx)
(ii)
Given that k = 2 min^-1
plug the value of k in equation (1), we get
Half life, t _½ = 0.693/ 2 = 30.35 min (approx)
(iii)
Given that k = 4 years⁻¹
plug the value of k in equation (1), we get
Half life, t _½ = 0.693/ 4 = 0.173 years (approx)