The half-life of a first-order reaction can be calculated using the formula t\(\frac{1}{2}\) = \(\frac{0.693}{k}\)

Where t\(\frac{1}{2}\) = 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\(^{-3}\) sec\(^{-1}\)

t\(\frac{1}{2}\) = \(\frac{0.693}{k}\)  = \(\frac{0.693}{4.5 x 10\(^{-3}\)}\)

  t\(\frac{1}{2}\)  = 154 s