What are the advantages of using a solvent pair for recrystallization? Select all that apply.
A) You can control the solubility of the substance in the mixed solvent.
B) You don't have to know the exact amounts of the solvents needed.
C) You can quickly make the solution supersaturated by adding more of the solvent with less dissolving power.
D) You can quickly make the solution supersaturated by adding more of the solvent with greater dissolving power.
E) You can calculate the precise amounts of the solvent needed for recrystallization.
I chose B and E but got it wrong. I'm not sure if it's because I chose the wrong ones, or I didn't choose all of the correct answers.
I've looked through my notes and textbooks many times, but I'm still a bit confused about this. Please help!
A,B, C
i think its A,B,C
The correct answers to the question about the advantages of using a solvent pair for recrystallization are:
A) You can control the solubility of the substance in the mixed solvent.
D) You can quickly make the solution supersaturated by adding more of the solvent with greater dissolving power.
Let's go through each option to understand why A and D are the correct answers:
A) You can control the solubility of the substance in the mixed solvent.
- When using a solvent pair, you can adjust the ratio of solvents to control the solubility of the substance. This allows for better control over the recrystallization process.
B) You don't have to know the exact amounts of the solvents needed.
- This is not an advantage of using a solvent pair. It is generally necessary to know the approximate amounts of solvents needed to achieve the desired solubility characteristics.
C) You can quickly make the solution supersaturated by adding more of the solvent with less dissolving power.
- This option is incorrect. The idea of quickly making the solution supersaturated is not a characteristic advantage of using a solvent pair. Supersaturation is usually achieved by cooling the solution.
D) You can quickly make the solution supersaturated by adding more of the solvent with greater dissolving power.
- This is a correct advantage of using a solvent pair. Adding more of the solvent with greater dissolving power allows for the rapid formation of a supersaturated solution, which can promote the formation of large, pure crystals during recrystallization.
E) You can calculate the precise amounts of the solvent needed for recrystallization.
- This option is incorrect. While it is possible to calculate approximate amounts of solvents needed for recrystallization, it is not specific to using a solvent pair. The exact amounts are often determined by experimental considerations, such as solubility tests and observations.
So, the correct answers are A) You can control the solubility of the substance in the mixed solvent, and D) You can quickly make the solution supersaturated by adding more of the solvent with greater dissolving power.
Recrystallization is a technique used to purify solid compounds. It involves dissolving the compound in a suitable solvent and then allowing it to slowly crystallize out. Using a solvent pair, which is a mixture of two solvents, can offer several advantages. Let's go through each option to determine the correct answers:
A) You can control the solubility of the substance in the mixed solvent.
This statement is true. By combining two solvents with different dissolving power, you can adjust the solubility of the compound. A selective solvent pair can ensure that the desired compound is soluble at high temperatures while insoluble at low temperatures, maximizing the purification process.
B) You don't have to know the exact amounts of the solvents needed.
This statement is incorrect. When using a solvent pair for recrystallization, it is crucial to know the precise proportions of each solvent. The ratio of solvents determines the dissolving power, so the amounts used affect the success of the recrystallization process.
C) You can quickly make the solution supersaturated by adding more of the solvent with less dissolving power.
This statement is true. By adding more of the solvent with less dissolving power, you can create a supersaturated solution quickly. Supersaturation occurs when the solvent can no longer dissolve the compound, causing it to precipitate out as crystals.
D) You can quickly make the solution supersaturated by adding more of the solvent with greater dissolving power.
This statement is incorrect. Adding more of the solvent with greater dissolving power would have the opposite effect. It would increase the solubility of the compound, making it less likely to crystallize and defeating the purpose of recrystallization.
E) You can calculate the precise amounts of the solvent needed for recrystallization.
This statement is incorrect. Determining the precise amounts of solvents for a solvent pair can be challenging and must be done carefully. It often requires prior experimental determination or extensive literature research for a specific compound.
Based on this analysis, the correct answers should be A and C. By using a solvent pair, you can control the solubility of the compound and quickly create a supersaturated solution by adding more of the solvent with less dissolving power.