What is the mass of 8.90 moles of magnesium chloride, MgCl2?

Express your answer numerically in grams.

Mass = mol x Mr

= 8.90 x (24.3 + (2) (35.5))

= 848.17g

Moles = weight of the given compound / molecular mass of that compound. Therefore Weight of MgCl2 = moles of MgCl2 x molecular mass of MgCl2 = 8.90 moles x (molecular weight of Mg + 2 x molecular weight of Cl) = 8.90 x (24 + 2x 35.5) ~ 845. 5gm.