Answer:
34.7s elapse before the concentration of A has fallen to 0.30 M
Explanation:
A reaction that is first order follows the equation:
ln [A] = ln [A]₀ - kt
Where [A] is concentration of A (0.30M) in time t, and [A]₀ is initial concentration (2.00M). K is reaction rate constant (0.05s⁻¹).
Replacing:
ln [0.30] = ln [2.00] - 0.05s⁻¹t
t = 34.7s elapse before the concentration of A has fallen to 0.30 M