Which of the following statements is /are true?

Answer
a.
None of he above.
b.
Impurities in a solvent raise the freezing point of that solvent
c.
All of the above
d.
Non-volatile impurities lower the boiling point of a solvent
e.
Ions lower the vapor pressure of a solvent more than molecules do.

None are true.

To determine which of the statements is/are true, let's analyze each statement:

a. None of the above.
This statement states that none of the other options are correct. This means that none of the statements b, c, d, or e are true.

b. Impurities in a solvent raise the freezing point of that solvent.
This is a true statement. Adding impurities to a solvent increases the boiling point of the solvent. This is known as boiling point elevation. The presence of impurities disrupts the regular arrangement of solvent molecules, making it more difficult for them to form a crystal lattice during freezing.

c. All of the above.
Since statement a is incorrect (none of the statements are true), this option is incorrect. Therefore, statement c is not true.

d. Non-volatile impurities lower the boiling point of a solvent.
This is an incorrect statement. Non-volatile impurities actually raise the boiling point of a solvent, not lower it. The presence of non-volatile impurities limits the escape of solvent molecules during boiling, causing an increase in boiling temperature, known as boiling point elevation.

e. Ions lower the vapor pressure of a solvent more than molecules do.
This statement is true. Ions have a stronger effect on lowering the vapor pressure of a solvent compared to molecules. This is due to the interaction between ions and solvent molecules in a solution. The presence of ions disrupts the attractive forces between solvent molecules, reducing their ability to escape into the vapor phase, and thus, lowering the vapor pressure.

In conclusion, the correct answer is b. Impurities in a solvent raise the freezing point of that solvent.