How many moles of electron weight one kilogram ?

$\begin{array}{l}\mathrm{Mass}\mathrm{of}\mathrm{an}\mathrm{electron}=9.108\times {10}^{-31}\mathrm{kg}\\ \mathrm{Thus},9.108\times {10}^{-31}\mathrm{kg}\mathrm{of}\mathrm{electron}\mathrm{contain}\\ =\frac{1}{6.023\times {10}^{23}}\mathrm{moles}\\ \therefore 1\mathrm{kg}\mathrm{of}\mathrm{electrons}\mathrm{will}\mathrm{contain}\\ =\frac{1}{6.023\times {10}^{23}}\times \frac{1}{9.108\times {10}^{-31}}\mathrm{moles}\\ =\frac{1}{6.023\times 9.108}\times {10}^8\mathrm{moles}\end{array}$