Solubility curves
2 marks · NormalA student mixes 8.0 g of a salt with 40.0 g of water at 30°C. After stirring, some solid remains undissolved. Use the solubility equation to calculate the solubility (in g per 100 g water) of the salt at 30°C for this experiment.
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20 g per 100 g water
Must show: Substitution of values, Correct units
Also accept: 20; 20g/100g; 20 g/100g; 20 grams per 100 grams water
Common mistakes: Incorrectly using the wrong values for mass solute or mass water; incorrect units
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Marking points
M1 · 1 mark · Writes correct solubility equation and substitutes values: (8.0 / 40.0) × 100.
A1 · 1 mark · Calculates correct answer: 20 g per 100 g water (with or without units).
Worked solution
Solubility (g per 100 g water) = (mass of solute / mass of solvent) × 100
So the solubility is 20 g per 100 g water.