Describe a test to identify calcium ions. Give the result of the test.

Describe a test to identify chloride ions. Give the result of the test.

The student determined the concentration of calcium chloride in the salt solution using the following method:

1. Weigh an empty evaporating basin.
2. Add $25.0{cm}^3$ of the salt solution into the evaporating basin.
3. Heat the evaporating basin and contents.
4. Weigh the evaporating basin and contents.
5. Repeat steps 3 to 4 until there is no further change in mass.
6. Repeat steps 1 to 5 three more times.

Why did the student heat the evaporating basin and contents until the mass did not change?

How did the student calculate the mass of solid calcium chloride remaining after steps 1 to 5?

Select one option:

• Option A: $Mass\; of25.0{cm}^{3}of\; salt\; solution+mass\; of\; empty\; evaporating\; basin$
• Option B: $Mass\; of25.0{cm}^{3}of\; salt\; solution-mass\; of\; empty\; evaporating\; basin$
• Option C: $Mass\; of\; evaporating\; basin\; and\; dry\; contents+mass\; of\; empty\; evaporating\; basin$
• Option D: $Mass\; of\; evaporating\; basin\; and\; dry\; contents-mass\; of\; empty\; evaporating\; basin$

The student calculated the concentration of calcium chloride in the salt solution. Table 1 shows the results:

The percentage by mass of calcium ions in calcium chloride is $36.1\%$.

Calculate the mean concentration of calcium ions in the salt solution.