How many grams of MgCl2 would be required to make 440 g of magnesium ?
440 g Mg x (molar mass MgCl2/atomic mass Mg) = ?
Another way to look at this is
%Mg in MgCl2 is (atomic mass Mg/molar mass MgCl2) = approx 25.5%
Then 0.255 x g MgCl2 = 440.
Solve for g MgCl2.
