An ionic compound MCl is simultaneously doped with ${10}^{-6}mole\%MC{l}_{2}and{10}^{-7}mole\%QC{l}_3.$The number of cationic vacancies in 2 moles of MCl is 

For every ${\mathrm{MCl}}_2$ one cation vacancy is produced and for every ${\mathrm{QCl}}_3$ two cationic vacancies are produced. 

Number of cationic vacancies

$\begin{array}{l}=\frac{{10}^{-6}}{100}\times 2\times 6\times {10}^{23}+\frac{{10}^{-7}}{100}\times 2\times 2\times 6\times {10}^{23}\\ =12\times {10}^{15}+24\times {10}^{14}\end{array}$

$\begin{array}{l}=\left(120+24\right)\times {10}^{14}\\ =1.44\times {10}^{16}\end{array}$