Consider the crystallization of sulfanilamide from 95% ethyl alcohol. If impure
sulfanilamide is dissolved in the minimum amount of 95% ethyl alcohol at 40°C
rather than 78°C (the boiling point of ethyl alcohol), how would this affect the
percent recovery of pure sulfanilamide? Explain your answer.
Isn't it less soluble at 40 C?
To understand how the change in temperature would affect the percent recovery of pure sulfanilamide, we first need to understand the concept of solubility.
Solubility refers to how much of a solute (in this case, sulfanilamide) can dissolve in a given solvent (ethyl alcohol) at a specific temperature. Generally, solubility increases with temperature, meaning that more solute can dissolve as the temperature increases.
In the case of sulfanilamide, it has a higher solubility in hot ethyl alcohol than in cold ethyl alcohol. This means that sulfanilamide would be more soluble in 78°C ethyl alcohol compared to 40°C ethyl alcohol.
Now, let's consider the crystallization process. When a hot solution of sulfanilamide in ethyl alcohol cools down, the solubility decreases, causing the excess sulfanilamide to form crystals. These crystals can be separated from the solution, resulting in a purer form of sulfanilamide.
However, if the impure sulfanilamide is dissolved in the minimum amount of 40°C ethyl alcohol instead of 78°C ethyl alcohol, the lower temperature would result in a lower solubility of sulfanilamide. This means that less sulfanilamide would dissolve in 40°C ethyl alcohol compared to 78°C ethyl alcohol.
Consequently, when the solution is cooled to induce crystallization, there would be a smaller amount of sulfanilamide in the solution available to form crystals. As a result, the percent recovery of pure sulfanilamide would likely be lower in the case of using 40°C ethyl alcohol compared to using 78°C ethyl alcohol.
In summary, using a lower temperature for dissolving impure sulfanilamide in 95% ethyl alcohol would result in a decreased solubility of sulfanilamide, leading to a lower percent recovery of pure sulfanilamide during the crystallization process.