Question

A solution contains an unknown amount of dissolved magnesium. Addition of 3.38×10−2mol of Na2CO3 causes complete precipitation of all of the magnesium.

What mass of magnesium was dissolved in this solution?

Answer 1

Mg ^2+(aq) + Na2CO3(aq) ==> MgCO3(s) + 2Na^2+
mols Na2CO3 = 0.0338
mols Mg = mols Na2CO3 (look at the coefficients in the balanced equation.
g Mg = mols Mg x atomic mass Mg = ?

Answer 2

2.5