Question

Ca+Cl2 gives CaCl2. Calculate the mass of chlorine left unreacted when 80g of calcium reacts with 150g of chlorine to form 222g of calcium chloride.

Answer 1

molar mass of Ca = 40g
molar mass of chlorine = 35.5g
So, Cl2 = 35.5 x 2 = 71g
molar mass of CaCl2 = 111g

So, 40g of Ca reacts with 71g of Cl2 to form 111g of CaCl2.
=> 80g of Ca reacts with 142g of of Cl2 to form 222g of CaCl2. (double)
Mass of Chlorine left out = 150 - 142 = 8g