Question

A student has three solutions of CsCI at 20 °C. The student tests each solution by adding a small amount of CCI to each solution. The results of each test are recorded in the table below.

Solution
Result
1
More crystals than were added appear at the bottom of the flask.
2
Crystals added settled at the bottom of the flask.
3
No visible solute appears at the bottom of the flask. Based on these results, describe the saturation of each solution before the tests were performed. Explain your reasoning.
Part B
After testing Solution 1 and observing the results, the student cooled Solution 1 to 10 °C. During the cooling, no additional solute came out of the solution.
- Describe the saturation of Solution 1 after it is cooled to 10 °C. Explain your reasoning.

Answer 1

Part A:

Based on the results of the tests, we can describe the saturation of each solution before the tests were performed as follows:

- Solution 1: Supersaturated. The fact that more crystals than were added appeared at the bottom of the flask indicates that the solution was already supersaturated before the test. The addition of more solute caused the excess solute to come out of the solution and form crystals.

- Solution 2: Saturated. The fact that the crystals added settled at the bottom of the flask indicates that the solution was already saturated before the test. The addition of more solute did not cause any additional solute to come out of the solution.

- Solution 3: Unsaturated. The fact that no visible solute appeared at the bottom of the flask indicates that the solution was unsaturated before the test. The addition of more solute did not cause any additional solute to come out of the solution.

Part B:

When the student cooled Solution 1 to 10 °C, no additional solute came out of the solution. This suggests that Solution 1 was already in a stable, supersaturated state before it was cooled. The excess solute had already come out of the solution and formed crystals, so further cooling did not cause any additional solute to come out. Therefore, we can describe the saturation of Solution 1 after it was cooled to 10 °C as supersaturated, and the excess solute had already crystallized out of the solution.