Question

If the rate constant for a first order reaction is k, the time (t) required for the completion of 99% of the reaction is given by:

• A. t = 0.693/k
  
• B. t = 6.909/k
  
• C. t = 4.606/k
  
• D. t = 2.303/k

Answer 1

The correct option is C t = 4.606/k


First order rate constant is given as,
k = $\frac{2.303}{t}$ log$\frac{100}{1}$

=$\frac{2.303}{t}$log${10}^2$

= $\frac{2.303}{t}$ 2 $\log 10$

= $\frac{4.606}{k}$