[Win,odd Dhamnekar]

Suppose you are presented with a clear solution of sodium thiosulfate, Na₂S₂O₃. How could you determine whether the solution is unsaturated, saturated, or supersaturated?

My answer:

To determine whether a solution of sodium thiosulfate ([itex] \text{Na}_2\text{S}_2\text{O}_3 [/itex]) is unsaturated, saturated, or supersaturated, you can follow these steps:

1. Add More Solute:
   - Unsaturated Solution: If you add more sodium thiosulfate to the solution and it dissolves, the solution is unsaturated. This means it can still dissolve more solute.
   - Saturated Solution: If you add more sodium thiosulfate and it does not dissolve, the solution is saturated. This means it has reached its maximum solubility at that temperature.
   - Supersaturated Solution: If you add a small crystal of sodium thiosulfate and it causes rapid crystallization of the excess solute, the solution is supersaturated. This means it contains more solute than it can normally hold at that temperature.

2. Temperature Change:
   - Heating: Heat the solution and see if more solute dissolves. If it does, the solution was likely saturated or supersaturated at the lower temperature.
   - Cooling: Cool the solution and observe if crystals form. If crystals form upon cooling, the solution was supersaturated.

3. Observation:
   - Clear Solution: If the solution remains clear after adding more solute, it is unsaturated.
   - Precipitation: If the solution becomes cloudy or precipitate forms after adding more solute, it is saturated or supersaturated.

By using these methods, you can determine the saturation state of your sodium thiosulfate solution.