Number of electrons in 1 molecule of Na2SO4.5H2O=120
120×6.022×1023 electrons are present in 1 mole of Na2SO4.5H2O
2.2×1010 electrons will be present in 2.2×1010120×6.022×1023 moles of Na2SO4.5H2O
=3.04×10−16 moles of Na2SO4.5H2O
Mass of Na2SO4.5H2O=no.of moles×molar mass
=3.04×10−16×232=7.05×10−14 g