Basics
Solubility refers to the ability of a substance (solute) to dissolve in another substance (solvent).
When it comes to test questions, the solute is often some type of salt and the solvent is often water.
The image above shows the solubility of different types of salt depending on water temperature.
Salts with a straight line [NaNO3, KCl, NaCl] show a constant rate of change in solubility.
Salts with a curved line [K2Cr2O7, Ce2(SO4)3] show a changing rate of change in solubility.
Question
Which salt has the highest solubility at 30°?
Answer
NaNO3
Answer Process
At 30°, NaNO3 has a solubility of 95, highest by far among the various salts.
Question
Which salt’s solubility decreases with increasing temperature before leveling off?
Answer
Ce2(SO4)3
Answer Process
At 0°, Ce2(SO4)3 has a solubility of approximately 18 before it decreases with increasing temperature, leveling off at a solubility of approximately 4.
Question
Which salt’s solubility barely increases with increasing temperature?
Answer
NaCl
Answer Process
At 0°, NaCl has a solubility of 35; at 100°, NaCl has a solubility that has barely risen to 40.
Practice – Questions
1. Which salt has the highest solubility at 90°?
A. NaCl
B. KCl
C. Ce2(SO4)3
D. K2Cr2O7
2. Which salt has the lowest solubility at 90°?
A. NaCl
B. KCl
C. Ce2(SO4)3
D. K2Cr2O7
3. Which salt’s solubility shows a changing rate of change?
A. NaCl
B. KCl
C. Ce2(SO4)3
D. NaNO3
4. Which salt’s solubility shows a changing rate of change?
A. NaCl
B. K2Cr2O7
C. KCl
D. NaNO3
4. Which salt has the highest solubility in the image?
A. NaNO3
B. K2Cr2O7
C. KCl
D. NaCl
Practice – Answers
1. D. K2Cr2O7
2. C. Ce2(SO4)3
3. C. Ce2(SO4)3
4. B. K2Cr2O7
5. A. NaNO3