Measuring solubility [chemistry only]
4 marks · NormalThe graph below shows the solubility curves of two substances, ammonium chloride and sodium chloride, in water.
Compare how the solubility of ammonium chloride and sodium chloride changes as temperature increases.
Estimate the solubility of ammonium chloride at 50°C using the graph.
Which substance is more soluble at 0°C?
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
(a) Ammonium chloride's solubility increases much more with temperature compared to sodium chloride, whose solubility hardly changes. · must show Identifies greater increase for ammonium chloride, Notes little change for NaCl
(b) About 55 g/100 g water · must show Estimate from graph
(c) Sodium chloride · must show Identifies NaCl
Also accept: Allow other estimates for part (b) in the range 53–57 g/100 g.
Common mistakes: Stating sodium chloride's solubility rises quickly with temperature.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States ammonium chloride's solubility increases more with temperature than sodium chloride.
B1 (a) · 1 mark · Mentions sodium chloride has little change in solubility.
A1 (b) · 1 mark · Estimates ammonium chloride's solubility at 50°C in the range 53–57 g/100 g water.
B1 (c) · 1 mark · Gives sodium chloride as the more soluble at 0°C.
Worked solution
a) Ammonium chloride's solubility increases rapidly as temperature increases. Sodium chloride's solubility changes very little with temperature. b) From the graph at 50°C, ammonium chloride's solubility is about 55 g/100 g water. c) Sodium chloride is more soluble at 0°C (36 g/100 g vs 29 g/100 g).