What mass of salt is obtained by the interaction of 100 grams of magnesium

What mass of salt is obtained by the interaction of 100 grams of magnesium oxide containing 5% impurities with phosphoric acid?

3MgO + 2H3PO4 = Mg3 (PO4) 2 + 3H2O.
1) Find the mass of impurities: 5 * 100/100 = 5g.
2) Find the mass of pure oxide substance: 100 – 5 = 95g.
3) Determine the molar mass of magnesium oxide according to the periodic table: 24 + 16 = 40.
4) Calculate the amount of magnesium oxide substance: 95/40 = 2.375 mol.
5) According to the reaction equation, there is one mole of the desired salt per three moles of oxide. This means that the amount of magnesium phosphate substance is: 2.375 * 3 = 7.125 mol.
6) Molar mass of magnesium phosphate: 263.
7) The mass of phosphate is: 263 * 7.125 = 1681.5 g – the answer.