Solubility curves
3 marks · EasyThe solubility curve for barium chloride shows that its solubility is 37 g per 100 g water at 60°C, and 29 g per 100 g water at 30°C.
How many grams of barium chloride will dissolve in 40 g of water at 60°C?
What is the maximum temperature at which 10 g of barium chloride will just dissolve in 20 g of water?
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(a) 14.8 g
(b) 40°C
Common mistakes: Forgetting to scale solubility for non-100 g water
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Marking points
M1 (a) · 1 mark · Scales the solubility for 40 g water: 37 ÷ 100 × 40.
A1 (a) · 1 mark · Gives 14.8 g as the answer (rounded). (follow-through)
B1 (b) · 1 mark · Estimates or calculates that 10 g in 20 g water corresponds to 50 g per 100 g, which occurs just below 60°C, so answer is 40°C (accept 38–42°C).
Worked solution
a) 37 ÷ 100 × 40 = 14.8 g will dissolve in 40 g water at 60°C.
b) 10 g in 20 g water = 50 g per 100 g water (as 10÷20×100=50). Looking at the solubility curve: at 60°C, solubility is 37 g/100 g, at 30°C it is 29 g/100 g; 50 is above these but would be around 40°C by interpolation.