If a solute is very soluble in a solvent (ethanol), why doesn't crystallization occur?
I attempted to recrystallize 14 g of solute A in 30 mL of ethanol, but crystallization didn't occur. Why?
Is it because a) the solution is supersaturated or b) because there is too much solvent? How can I tell which of the two reasons is to blame?
More than likely it isn't supersaturated. The probable cause is too much solvent. Let some of the solvent evaporate.
If you want to check to see if it is supersaturated, drop a crystal of the solute into the solution. If it is supersaturated the solute should crystallize immediately.
thank you!
In order to determine why crystallization did not occur in your experiment, we need to consider the factors that affect the formation of crystals in a solution.
Crystallization occurs when solute molecules come together in a specific arrangement to form a solid crystal lattice. However, for crystallization to happen, certain conditions need to be met.
One important factor is the solubility of the solute in the solvent. In your case, you mentioned that the solute (A) is very soluble in ethanol. This means that the solute molecules are easily dispersed and completely dissolved in the ethanol solvent.
If a solute is highly soluble in a solvent, it usually means that the solute molecules have a strong affinity for the solvent molecules, leading to a stable solution. This can prevent the formation of a supersaturated solution, which is necessary for the spontaneous formation of crystals.
A supersaturated solution occurs when more solute is dissolved in a solvent than its equilibrium solubility at a given temperature. In such a state, the solution becomes unstable and tends to crystallize, resulting in the formation of solid crystals.
To determine whether the lack of crystallization in your experiment is due to the solution being supersaturated or the presence of an excess amount of solvent, you can try the following steps:
1. Increase the concentration of solute A in the solvent: Add more solute to the solvent, and stir the mixture to dissolve it. If you continue to add solute beyond its saturation point, the solution may become supersaturated, increasing the chances of crystallization.
2. Decrease the amount of solvent: Reduce the volume of ethanol in the solution. By reducing the amount of solvent, you increase the concentration of solute in the remaining solution, and this may promote the formation of crystals.
By performing these steps, you can evaluate whether a supersaturated solution or excess solvent concentration was the reason for the lack of crystallization. If increasing the concentration of solute or reducing the amount of solvent leads to the formation of crystals, it suggests that the original solution was not supersaturated enough. On the other hand, if no crystals form even after making these adjustments, it is more likely that the high solubility of the solute in the solvent is inhibiting crystallization.