A first order reaction with respect to reactant A , has a rate constant text6 textmin- 1 . If we start with [ textA] = 0.5 textmol textL- 1 , when would [.A]. reach the value 0.05 textmol textL- 1

Question

A first order reaction with respect to reactant A , has a rate constant text6 textmin- 1 . If we start with [ textA] = 0.5 textmol textL- 1 , when would [.A]. reach the value 0.05 textmol textL- 1 (A) 0.384 min (B) 0.15 min (C) 3 min (D) 3.84 min

Tardigrade Admin · Accepted Answer

We know that for first order kinetics k=(2.303/t)log(a/a - x) ( texta-x) = 0.05 textmol ( textL)- 1 6=(2.303/t)log(0.5/0.05) or textt = (2.303/6) textlog (0.5/0.05) = (2.303/6) = 0.384 textmin

Q. A first order reaction with respect to reactant $A$ , has a rate constant $6 min^{- 1} .$ If we start with $[A] = 0.5 mol L^{- 1}$ , when would $[A]$ reach the value $0.05 mol L^{- 1}$

0.384 min

0.15 min

3 min

3.84 min

We know that for first order kinetics
$k = \frac{2.303}{t} l o g \frac{a}{a - x}$
$(a-x) = 0.05 mol (L)^{- 1}$
$6 = \frac{2.303}{t} l o g \frac{0.5}{0.05}$
or $t = \frac{2.303}{6} log \frac{0.5}{0.05} = \frac{2.303}{6} = 0.384 min$

Q. A first order reaction with respect to reactant A , has a rate constant 6min−1. If we start with [A]=0.5molL−1 , when would [A] reach the value 0.05molL−1