Measuring solubility [chemistry only]
2 marks · EasyAt 25°C, the solubility of potassium nitrate is 38 g per 100 g of water. Calculate the maximum mass of potassium nitrate that will dissolve in 250 g of water at this temperature. Show your working.
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95 g (±0.5)
Common mistakes: dividing instead of multiplying; using 250/38 instead of 38/100 × 250
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Marking points
M1 · 1 mark · Shows correct method to scale solubility to 250 g of water (e.g., 38 × 2.5 or 38/100 × 250).
A1 · 1 mark · Correct final answer: 95 g. (follow-through)
Worked solution
Solubility for 100 g water = 38 g; for 250 g water: