A solution contains an unknown amount of dissolved magnesium (Mg 2+). Addition of 5.50×10^−2 mol of Na2CO3 causes complete precipitation of all of the magnesium. what mass of the magnesium was dissolved in the solution? answer in unit g.

Answer 1

First write and balance the equation.
Mg^+2 + Na2CO3 ==> 2Na^+ + MgCO3.

You know how many moles Na2CO3 were used. Convert mole Na2CO3 to moles Mg using the coefficients in the balanced equation. Then convert moles Mg to grams. g = moles x molar mass.