if you were not told which solvent to use in the recrystallization experiment, how would you determine a suitable recrystallization solvent ?

trial and error

The ideal solvent for recrystallization is one in which the solute has high solubility at high temperature and low solubility at low temperature. You could try to look up solubilities in chemistry handbooks or experiment with different solvents. If you have to do that you might include mixed solvents.

If temperature differences do not produce much difference in solubility, you might have to bring about recrystallization by solvent evaporation. The solute must have high solubility in the solvent.

If you do not have any information or recommendations on which solvent to use for recrystallization, you can adopt a systematic approach to determine a suitable solvent. Here's a step-by-step process to follow:

1. Begin with a list of common solvents: Start by making a list of commonly used solvents for recrystallization, such as water, ethanol, methanol, acetone, dichloromethane, and hexane. This list is not exhaustive, but it provides a good starting point.

2. Consider solubility: Look up the compound you want to recrystallize and determine its solubility in different solvents. You can find this information in chemical databases, reference books, or online resources. Note down the solvents in which the compound is known to be soluble to some extent.

3. Determine temperature effects: Some compounds exhibit different solubilities at varying temperatures. Find out if the solubility of your compound changes significantly with temperature. You can refer to solubility curves or consult scientific literature.

4. Determine impurity solubility: Identify the main impurities present in your compound. Look for solvents in which these impurities are readily soluble. It is essential to choose a solvent that will dissolve the impurities but leave behind the pure compound during recrystallization.

5. Check for chemical compatibility: Ensure that the solvent you select is chemically compatible with the compound you want to purify. Some compounds may degrade or react with certain solvents, leading to unwanted side reactions or loss of the desired compound.

6. Perform solubility testing: Prepare small test tubes or containers and add a small quantity of your compound to each. Add a different solvent to each container and mix thoroughly. Observe whether your compound dissolves or remains insoluble in each solvent. Record your observations.

7. Evaluate solvent effectiveness: Based on the solubility testing, identify solvents in which your compound has good solubility and impurities show poor solubility. Additionally, consider factors such as ease of removal of the solvent after recrystallization and the desired crystal properties (e.g., size, shape, and purity).

8. Test selected solvents: Once you have identified potential solvents from the previous step, perform a small-scale recrystallization experiment using each solvent. Compare the results, such as crystal yield, purity, and characteristics, to determine the most suitable solvent.

By following this systematic approach, you can evaluate different solvents and determine a suitable one for recrystallization when you haven't been explicitly told which solvent to use.