Question

Problem : 30 g of magnesium and 30 g of oxygen are reacted. Calculate the mass of Mgo
produced. Which is the limiting reagent? Atomic mass of mg = 24.​

Answer 1

The reaction is 2Mg+O2→2MgO.

Thus, 2 moles of magnesium react with 1 mole of oxygen to form 2 moles of magnesium oxide.

The molecular weights of magnesium, oxygen and magnesium oxide are 24,32 and 40 g respectively.

30 g of magnesium and 30 g of oxygen corresponds to 1.25 and 0.9375 moles respectively.

1.25 moles of magnesium will react with 0.625moles of oxygen to produce 1.25 moles of magnesium oxide.

Thus, 30 g of magnesium will react with 20 g of oxygen to produce 50 g of magnesium oxide.

Thus, the resulting mixture contains 50 g of magnesium oxide and 30−20=10 g of oxygen.