What is the rate constant of a first-order reaction that takes 143 seconds for the reactant concentration to drop to half of its initial value?

k = 4.85 x 10⁻³ / s

Explanation:

For a first order reaction we have two very important equations we need to memorize:

ln ( N/N₀ ) = -kt

and,

0.693/ k = t₁/₂

where k is the rate constant and t i is the halflife which can be derived from the first equation.

0.693/ k = t₁/₂   ⇒  k = 0.693 / t₁/₂  

k = 0.693 / 143 s = 4.85 x 10⁻³ / s

the correct answer is a

helloi think dog cat bunny dog cat bunny dog cat bunny