${\mathrm{PCl}}_5\left(\mathrm{g}\right)\to {\mathrm{PCl}}_3\left(\mathrm{g}\right)+{\mathrm{Cl}}_2\left(\mathrm{g}\right)$

In the above first order reaction the concentration of ${\mathrm{PCl}}_5$ reduces from initial concentration $50 \mathrm{mol}{ \mathrm{L}}^{-1}$ to $10 \mathrm{mol}{ \mathrm{L}}^{-1}$ in $120$ minutes at $300 \mathrm{K}.$ The rate constant for the reaction at $300 \mathrm{K}$ is $\mathrm{x}\times {10}^{-2}{ \min }^{-1}.$ The value of $\mathrm{x}$ is __________.

[Given $\log 5=0.6989$]

Hence, the correct answer is 1.