Recrystallization: Melting & Boiling Points

In summary, during recrystallization, it is important for the melting point of the solute to be lower than the boiling point of the solvent. This ensures that the solute will remain in solid form during the boiling of the solvent, which is necessary for recrystallization to occur.
  • #1
tipton12
20
1
does anyone know why it is important to have the melting point of a solute not be higher than the boiling point of the solvent during recrystallization? --having a little trouble rationalizing this.
 
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  • #2
Is this not because the pattern will be from a liquid a solid and then to a gas if you decrease the temperature?

The Bob (2004 ©)
 
  • #3
Are u sure you're asking a right thing...?I mean according to me,it should be the other way around.The solvent (water,e.g.) must have the boiling point temp.less than solute's melting point,AT THE SAME PRESSURE...

Daniel.
 
  • #4
Ok, you're right dextercioby. I had it the other way around. Oops! But I still am not clear on the reasoning. Here is the website I read it from:
http://www.ux1.eiu.edu/%7Ecfthb/classes/2445/2003/Quiz2key.htm
 
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  • #5
I only assumed that if the bp of the solvent was higher thanthe mp of the solute than the compound you're trying to isolate will have already melted and mixed completely with the solvent.
 
  • #6
Nope,recrystallization of a solution means:
boiling of the solvent------------->recrystallization of the solute.
Since you want the solute to be solid (that means "recrystallization"),you need to boil the solvent.Ergo,its boiling point < the melting point of the solute (at the same pressure);

Daniel.
 

Related to Recrystallization: Melting & Boiling Points

1. What is recrystallization?

Recrystallization is a technique used in chemistry to purify solid compounds. It involves dissolving a solid in a solvent, then allowing the compound to crystallize out of the solution, leaving behind any impurities.

2. Why is recrystallization important in scientific research?

Recrystallization is important because it allows scientists to obtain pure compounds for use in experiments and analyses. Impurities can affect the results of experiments, so it is important to remove them through recrystallization.

3. How do melting and boiling points play a role in recrystallization?

The melting and boiling points of a compound are important in determining the appropriate solvent for recrystallization. The solvent should have a lower boiling point than the compound to be purified, and the compound should have a higher melting point than the solvent. This ensures that the compound will dissolve in the solvent at high temperatures, then recrystallize as the solution cools.

4. What factors can affect the success of a recrystallization procedure?

Some factors that can affect the success of a recrystallization procedure include the choice of solvent, the temperature and rate of cooling, and the amount of solid compound used. It is important to choose a solvent that is appropriate for the compound and to carefully control the temperature and cooling rate to produce pure crystals.

5. Is recrystallization the only method for purifying solid compounds?

No, there are other methods for purifying solid compounds, such as distillation and chromatography. However, recrystallization is often preferred because it is a simple and effective method for obtaining pure compounds. Additionally, some compounds may be sensitive to the high temperatures required for distillation, making recrystallization a better option for purification.

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