For a first-order reaction, the half-life ($t_{1/2}$) is calculated using the formula:

$t_{1/2} = \frac{0.693}{k}$

Given that the rate constant $k = 4.3 \times 10^{-5} \, \text{s}^{-1}$, we can substitute this value into the formula:

$t_{1/2} = \frac{0.693}{4.3 \times 10^{-5} \, \text{s}^{-1}}$

Calculating this gives:

$t_{1/2} \approx \frac{0.693}{4.3 \times 10^{-5}} \approx 1.61 \times 10^4 \, \text{s}$

So, the half-life of the reaction is approximately $1.61 \times 10^4$ seconds.