# NEET Chemistry Chemical Kinetics Questions Solved

BOARD

(q) A first order reaction is 15% completed in 20 minutes. How long will it take to complete 60% of the reaction?

a. 112.8min

b.120.7 min

c.100.4 min

d.140.7min

For the first order reaction

K =

First case: a = 100, $\mathcal{x}$ = 15, time, t = 20 minutes

(a-$\mathcal{x}$) = 100 - 15 = 85

........(1)

Second case : a=100, $\mathcal{x}$=60,  time,${t}_{60%}$= ?

(a-$\mathcal{x}$) = 100 - 60 = 40

.........(2)

Dividing equation (2) by (1), we get

$\frac{{t}_{60%}}{20}=\frac{\mathrm{log}\frac{100}{40}}{\mathrm{log}\frac{100}{85}}=\frac{\mathrm{log}100-\mathrm{log}40}{\mathrm{log}100-\mathrm{log}85}$

= $\frac{2.000-1.6021}{2.0000-1.9294}$

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