1. For the TBOH freezing point determination, what common errors might contribut
ID: 486538 • Letter: 1
Question
1.For the TBOH freezing point determination, what common errors might contribute to a false low value for the freezing point of pure TBOH? TBOH is tert-butyl alcohol
2.Will the freezing point of a solution (solute and solvent mixture) always be lower than the freezing point of the pure solvent?
3.Does the value of Kf (for TBOH) depend of the amount of the Benzoic acid used? Explain why?
4.Discuss what else you can do except adding more BA, or any solute into TBOH solution to decrease the freezing point for TBOH.
Explanation / Answer
1. Most common errors affecting freezing point of TBOH are, the thermometer is not calibrated before use. The system is not equilibriated before recording the freezing point of solution. TBOH easily picks up water, presence of large excess water, gives lower freezing point.
2. Yes, freezing point of solute and solvent mixture is always lower than the pure solvent as more heat is needed to be removed from the mixture to freeze it as compared to the pure solvent.
3. Kf is a constant and independent of ampunt of solute added to pure solvent. It is entirely dependent upon type of solvent. It is a physical constant like melting point, boiling points etc. for the solvent used.
4. Adding more water to TBOH will give a lower freezing point. Freezing point of water is lower than the freezing point of TBOH and thus as the volume of water in TBOH goes up, freezing point goes further down.
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