Measuring solubility [chemistry only]
5 marks · HardThe solubility curves below show the solubility of salt X and salt Y in water at different temperatures.
State which salt is more soluble in water at 30°C.
Calculate the difference in solubility between salt X and salt Y at 60°C.
Describe how the solubility of each salt changes as the temperature increases from 10°C to 70°C.
Explain why it is important to use the same amount of water when measuring the solubility of different salts.
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) Salt Y
(b) 27 g/100g water
(c) Salt X: solubility increases rapidly with temperature; Salt Y: solubility increases only slightly.
(d) To allow a fair comparison between solubilities.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correct salt stated: Salt Y.
B2 (b) · 1 mark · Correct calculation: (66−39) = 27 (g/100g water) at 60°C.
B3 (c) · 1 mark · Describes that salt X's solubility increases rapidly with temperature.
B4 (c) · 1 mark · Describes that salt Y's solubility increases only slightly with temperature.
B5 (d) · 1 mark · Explains that using the same amount of water is needed to compare solubilities fairly.
Worked solution
a) At 30°C, Salt Y has a solubility of 34 g/100g water; Salt X has 29 g/100g water. So, Salt Y is more soluble.
b) At 60°C, Salt X = 66 g/100g, Salt Y = 39 g/100g. Difference is 66 - 39 = 27 g/100g.
c) Salt X: solubility increases rapidly from 18 to 80 g/100g between 10°C and 70°C. Salt Y: solubility increases slowly from 32 to 41 g/100g.
d) Because solubility is defined as mass of solute per 100g water, using the same amount of water allows fair comparison between different salts.