1 Investigate the solubility of a solid in water at a specific temperature Flashcards
(9 cards)
Method to investigate how temperature affects solubility?
- Add excess ammonium chloride to 10 cm³ water in a boiling tube → forms a saturated solution
- Stir and place the tube in a 25 °C water bath for 5 min
- After 5 mins, check excess solid has settled and the temperature is 25 °C (with a thermometer)
- Pour some of the solution (not undissolved solid) into a pre-weighed empty evaporating basin
- Re-weigh basin then gently heat with a Bunsen burner to evaporate all water (avoid overheating, or ammonium chloride may turn to gas)
- Left with pure ammonium chloride + re-weigh again
- Repeat with water baths at 35 °C and 45 °C
- Use mass differences to calculate solubility at each temperature
- Plot solubility vs temperature to observe the trend
How will you know when ammonium chloride is in excess?
It will start to sink to the bottom of the tube
What happens if you heat the basin too strongly?
Some of the ammonium chloride might turn into a gas + escape -> causes mass of solid in the basin to decrease + your solubility value will be lower than it should be
What should you do after creating a saturated solution of ammonium chloride?
Stir the solution and place the boiling tube in a water bath set to 25 °C.
How do you ensure the solution reaches the correct temperature before continuing?
Wait 5 minutes and check with a thermometer to confirm it’s at 25 °C.
Why must you avoid pouring undissolved solid into the evaporating basin?
To ensure only the dissolved ammonium chloride is measured for solubility.
Why should the solution be heated gently?
To prevent ammonium chloride from turning into gas and escaping.
What do you do after pouring the solution into the evaporating basin?
Weigh the basin and its contents, then gently heat to evaporate all the water.
What should be done after all the water has evaporated from the basin?
Re-weigh the basin and solid to find the mass of dissolved ammonium chloride.
