Question

A 1.30 M solution of CaCl2 in water has a density of 1.11g/mL. What is the molality?

Answer 1

A 1.30 M solution of CaCl₂ in water has a density of 1.11g/mL. What is the molality?

Molecular mass of CaCl₂ = 110.98 g/mol (take 111 g/mol)

mass of 1.3 moles CaCl₂ = 1.3*111 = 144.3 g

Density of solution is 1.11 g/mL, thus mass of 1000 mL solution is = 1000 * 1.11 g = 1110 g

Thus, amount of water is, (1110 - 144.3) g = 965.7 g

So, 1.3 moles present in 965.7 g of water,

In 1000g of water, (1.3*1000/965.7) moles of CaCl₂ present = 1.346 moles

Molality of the solution is 1.346 m.