The half-life of a first-order reaction can be calculated using the formula t 12\;\frac{1}{2}21 = 0.693k\;\frac{0.693}{k}k0.693
Where t 12\;\frac{1}{2}21 = the half-life and k = the rate constant
From the question, we were given the value for k, which is the constant to be 4.5 x 10−3^{-3}−3 sec−1^{-1}−1
t 12\;\frac{1}{2}21 = 0.693k\;\frac{0.693}{k}k0.693 = 0.6934.5x10−3\;\frac{0.693}{4.5 x 10^{-3}}4.5x10−30.693}\)
t 12\;\frac{1}{2}21 = 154 s
