A chimpanzee was shown two A chimpanzee was shown two Calculate the molar mass o

Question

A chimpanzee was shown two A chimpanzee was shown two Calculate the molar mass of the unknown solute from the difference between the freezing point of the solution and the pure solvent. Report the molar mass determined from solution one (0.10 0.13 g of solute) and solution two (0.17- 0.20 g of solute). Calculate the mean and the RAD and comment on your precision. Answer the following questions in your report. 1. If the freezing point of the solution is recorded 0.2°C lower than the actual freezing point, will the molar mass determination for the unknown solid be too high or too low? Explain. 2. If a thermometer is miscalibrated to read 0.5 °C higher than the actual temperature over its entire scale, how will it affect the reported molar mass of the solute? Explain. 3. Cyclohexane has a relatively high vapor pressure. If some of the cyclohexane evaporates during the experiment, how will this affect the Air? How will this affect the reported molar mass of the unknown solute? Explain. 4. Why was a salt/ice bath used in this experiment instead of just an ice bath?

Explanation / Answer

1. Freezing point lowering is directly proportional to the molality of the solute in solution. If calculated freezing point lowering is less than actual one then calculated molality will be less. Molality is inversely proportional to molar mass of solute. Hence, the calculated molar mass will be higher than actual molar mass.

2. If the thermometer is miscalibrated then same temperature error will be there in reading the actual freezing point of the solvent and the freezing point of solution. The error will cancel out and in the experiment there will be no error in the calculation.

3. If cyclohexane evaporates , then molality of the solution will be less than actual. Freezing point lowering is directly proportional to the molality of the solute in solution. So, calculated delTf is less than actual one.

Molality is inversely proportional to molar mass of solute. Hence, the calculated molar mass will be higher than actual molar mass.

4. Ice/ salt bath has -15 0 c temperature which is much lower than the temperature of normal ice bath (0 0C) and is more useful to keep the low temperaure for longer time.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.