Question

At very high temperature HCl will decompose overtime to form gaseous hydrogen and chloride.

The reaction is second order in HCl and the rate constant is 15.5x10-7M-1s-1 If

the initial concentration of HCl is 0.200 M, what is the concentration of the remaining HCl after a reaction

time of 1 week? (Hint: How many seconds in a week?)

Answer 1

Sol :-

The integrated rate equation for second order reaction is :

kt = 1/[A]_t - 1/[A]₀ ................(1)

Here, K = Rate constant, which is give = 15.5 x 10^-7 M^-1s^-1

t = Time period, which is given = 1 week = 604800 s

[A]₀ = Initial concentration of reactants = 0.200 M

[A]_t = Concentration at time "t" = ?

Substitute all these values in equation (1) :

(15.5 x 10^-7 M^-1s^-1).(604800 s) = 1/[A]_t - 1/0.200 M

0.93744 M^-1 + 5.0 M^-1 = 1/[A]_t

5.93744 M^-1 = 1/[A]_t

Taking reciprocal on both the sides

[A]_t = 1/5.93744 M^-1

[A]_t = 0.168 M

Hence, Concentration = 0.168 M