Activity Project: Effect of Temperature on Solubility of Potassium Chloride (KCl)

Objective

To study how the solubility of potassium chloride (KCl) varies with temperature.

Materials Required

• Potassium chloride (KCl) sample
• Distilled water
• Beakers
• Thermometer
• Measuring cylinder
• Water bath or heating source
• Stirring rod
• Filter paper and funnel
• Conical flasks

Procedure

1. Take 100 mL of distilled water in a beaker and heat it to the desired temperature (e.g., 30°C, 40°C, 50°C, 60°C, 70°C, 80°C).
2. Add small amounts of KCl to the hot water while stirring until no more dissolves and the solution becomes saturated (undissolved salt remains).
3. Filter the saturated solution to remove undissolved salt.
4. Cool the solution slowly to room temperature and note temperature.
5. Weigh an evaporating dish and pour out a known volume (e.g., 25 mL) of the saturated solution into it.
6. Evaporate the water completely and weigh the residue to find the amount of dissolved KCl.
7. Repeat the above steps for different temperatures.
8. Calculate solubility in grams per 100 mL of water for each temperature and plot a solubility vs. temperature graph.

Observations

Temperature (°C)	Mass of KCl dissolved (g) per 100 mL Water	Observation
30	28	Saturated solution formed
40	34	Saturated solution formed
50	38	Saturated solution formed
60	44	Saturated solution formed
70	49	Saturated solution formed
80	56	Saturated solution formed

Result

Solubility of potassium chloride increases with temperature, which can be seen from the positive slope in the solubility vs. temperature graph.

Precautions

• Ensure accurate temperature measurement with a thermometer.
• Stir solution thoroughly to reach saturation.
• Cool solutions slowly to avoid premature crystallization.
• Weigh evaporating dish before and after evaporation carefully.
• Repeat measurements for better accuracy.