Question

Assuming that you have excess Na2CO3 (i.e., it is not the limiting reactant), how many grams of CaCl2•2H2O are needed to produce 2.5 g of CaCO3? Show your work.

Answer 1

Reaction:

Ca²⁺ (aq) + CO₃^2- (aq) --------> CaCO₃ (s)

From equation, one mole of Ca²⁺ required to produce one mole CaCO₃ .

One mole CaCl₂ 2H₂O contains one mole Ca²⁺.

Molar mass of CaCl₂ 2H₂O is 147 g/mol.

Molar mass of CaCO₃ is 100 g/mol.

Mass of CaCl₂ 2H₂O required to produce 2.5 g CaCO₃ is,

2.5 g CaCO₃ x ( 1 mol CaCO₃/ 100 g CaCO₃ ) x ( 1 mol Ca²⁺ / 1 mol CaCO₃ ) x ( 1 mol CaCl₂ 2H₂O/1 molCa²⁺ )x ( 147 g CaCl₂ 2H₂O/ 1 mol CaCl₂ 2H₂O) = 3.675 g = 3.7 g

So, the mass of CaCl₂ 2H₂O required to produced 2.5 g CaCO₃ is 3.7 g.