Question

1. Explain an experiment that you can carry out in the lab to establish the solubility of different compounds (10 marks)

Answer 1

Solution:

• The maximum amount of solute that can be dissolved in a particular solvent at a given temperature is called solubility of the solute and these solutions are called saturated solutions.
• Solubility of a solute can vary from solvent to solvent.

The experimental procedure to establish solubility of different solute is given below.

1. On a sheet of paper or with the use of a computer draw a table -1 with the contents as shown below.
2. Use a set up of a cup with stirring arrangement as well as thermometer.
3. Measure accurately 10 ml of solvent using a calibrated graduated cylinder and pour into a cup with stirring arrangement.
4. Start and set the stirrer to gentle agitation.
5. Weigh accurately to about 5 g of the solute and add it to the cup in several small portions of about 50 mg each using spatula.
6. Observe the cub to see that the previous portion is dissolved. Then add next portion of the solute.
7. If a crystal of the solute settle out of the mixture, then the solution is saturated.
8. If first 5 g is not enough, weigh another 5 g and carry out the experiment. This can be done till you get saturated solution.
9. Now, record the temperature. Reweigh the remaining solute accurately and record.
10. Divide the mass of the compound by the mass of the solvent and then multiply by 100 g to calculate the solubility in g/100g  
11. Repeat the procedure from 3 to 10 for different solute and different solvents and record the observation.

Table -1:

	Solute 1 at Temperature	Solute - 2 / Temperature
Solvent 1	....g / 100g at ...oC	....g / 100g at ...oC
Solvent 2	....g / 100g at ...oC	....g / 100g at ...oC

Precautions:

• Use clean glassware and apparatus.
• Make sure there is no spillage during the experiment.
• Make sure the weighing, measuring done accurately using calibrated instruments.