Seeking help with crystallization issues
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A saturated solution of a certain salt does not crystallize at room temperature; however, crystals form when the temperature is lowered, and these crystals do not dissolve again once the temperature returns to room level. I’d like to ask the experts: what is the reason for this? Is it because the solubility has changed?
After crystallization, it dissolves, and the heat energy required is higher than that released during precipitation. It means that for crystallization to dissolve, the temperature must be higher than room temperature
The solubility of a substance is affected by temperature
It is indeed affected by temperature, but there is no change in temperature before and after...
This post was last edited by w574869908 on 2016-11-23 at 13:58. So, is it possible for these precipitated crystals to continue growing at room temperature? Is the solution not a saturated solution anymore?
If the crystallized product is not of good quality, some seed crystals can be added
Do the precipitated crystals contain crystal water?
Crystallization has a metastable region; at temperatures where saturation is reached, crystals do not form. External conditions are required, such as the addition of seed crystals, the creation of debris by friction against the wall, or cooling to remove the heat of crystallization. Once this metastable region for crystallization is crossed, crystals begin to form:lol
Not sure; I don’t know if it contains crystal water............But the crystals that form directly should not contain any crystal water, right? . .
It depends on the specific product and its conditions; those that can precipitate directly may contain crystal water
For pure substances, solubility is a function of temperature; when the temperature remains constant, the solubility also stays constant. Crystallization occurs when the temperature drops, and crystallization happens again when the temperature is raised. The crystals that form as a result of a temperature drop may not be those of the original solute