Solubility curves

3 marks · Normal

The solubility curve below shows that at 60°C, the solubility of sodium sulfate is 50 g per 100 g of water. At 30°C, its solubility is 30 g per 100 g of water.

Calculate the maximum mass of sodium sulfate that will dissolve in 250 g of water at 60°C. Show your working.

Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.

Show answer

125 g (±1)

Must show: Set up proportion for mass of solute in given mass of water

Also accept: 125; 125.0; 125 g

Common mistakes: Using wrong value for solubility or mass of water

Show mark scheme and worked solution

Marking points

M1 · 1 mark · Writes down correct equation or sets up proportion: mass to dissolve = (solubility at 60°C) × (mass water) / 100.

M2 · 1 mark · Substitutes correct values: 50 × 250 / 100 or equivalent.

A1 · 1 mark · Arrives at correct answer: 125 g.

Worked solution

Maximum mass that dissolves = (solubility at 60°C in g/100g water) × (mass of water / 100 g)