Question

What will be the rate constant of a first order reaction,if it's half Life is given to be 20 min

Answer 1

A first order reaction is given by :-

Ln(R_o/R) = Kt

where,

R_o - original amount of substance

R - amount of substance left

K - rate constant

and t - is the time elapsed.

Now,

R_o = 2R

which means,

2.303 log(2) = kt

\(\frac{0.693}{t}\) = rate constant

\(\frac{0.693}{20 }\) =0.03465 min^-1

^{= 0.00575 sec-1}