$1 "mol" " Mg"("ClO"_4)_2$ contains :-
- $color(red)(1 "mol Mg atoms")$
- $color(blue)(2 "mol Cl atoms"$
- $color(green)(8 "mol O atoms"$
To find no. of moles of each element, we can multiply the above values by $7.7"mol"$
$color(red)(1 "mol Mg atoms")/(1 "mol" " Mg"("ClO"_4)_2)times7.7 "mol" " Mg"("ClO"_4)_2=1times7.7=7.7"moles"$
Similarly,
$color(blue)(2 "mol Cl atoms")/(1 "mol" " Mg"("ClO"_4)_2)times7.7 "mol" " Mg"("ClO"_4)_2=2times7.7=15.4"moles"$
$color(green)(8 "mol O atoms")/(1 "mol" " Mg"("ClO"_4)_2)times7.7 "mol" " Mg"("ClO"_4)_2=8times7.7=61.6"moles"$