Question

The initial concentration of reactant in a first-order reaction is 0.27 M. The rate constant for the reaction is 0.75 s−1. What is the concentration (in mol/L) of reactant after 1.5 seconds?

Answer 1

The first order reaction law of kinetics is $t=$ $2.303 \over k$ $log$ $a\over (a-x)$

Where t= time taken for the reaction $= 1.5$ seconds.

k= the rate constant $=0.75s^{-1}$

a is the initial amount of reactant $=0.27 M$

(a-x) is the amount left $= unknown$

$1.5=$ $2.303\over 0.75$ $log$ $0.75\over (a-x)$

$1.5=(3.071) log$ $2.7\over (a-x)$

$(a-x)=0.087$ mol/L

The amount of concentration left after $1.5$ seconds $=$ $0.087 mol/L$