Question

What molal solution is made when adding 90 grams of K2SO4 to 0.55 kg of water?

Answer 1

Morality is defined as number of moles of solute dissolved in per kg of solvent. 

It is denoted by m.

m = $\frac{number of moles of solute}{weight of solvent in kg}$

Moles of solute = weight of K₂SO₄$\div$ molar mass of K₂SO₄

Molar mass of K₂SO₄= 2×39 + 1×32 +4×16 =174g/mol

Moles of K₂SO₄= $\frac{ 90}{174}= 0.52 mole$

Now 

Molality = $\frac{0.52 mole}{0.55kg }= 0.96 molar$

The solution is 0.96 molar.