Question

Which of the following results from the presence of a solute in a given solvent?

A. The vapor pressure of the solution is lower than that of the pure solvent.

B. The boiling point of the solution is lower than that of the pure solvent.

C. The freezing point of the solution is higher than that of the pure solvent.

D. all of the above

Answer 1

Which of the following results from the presence of a solute in a given solvent?

Note that we must assume the solute is non-volatile, in order to answer this; otherwise, this will not apply

A. The vapor pressure of the solution is lower than that of the pure solvent.

True, since:

Pmix = Ppure - dP

dP can be moeddeled:

dP = xsolute * Psolvent

as xsolute increases, dP increases, therefore Pmix decreases

B. The boiling point of the solution is lower than that of the pure solvent.

this is FALSE , due to colligative properties... this will INCREASE

dTb = Kb*m

Kb = boiling point increase due to solut presence

m = molality

C. The freezing point of the solution is higher than that of the pure solvent.

FALSE; it will be LOWER... since there is colligative property of depression point the one can be modelled as:

-dTf = -Kf*m

in which, Kf = depression constant, typically depends on the solvent only;

dTf = depression of freezing temperature

m = molality of solute in solvent = mol of solute / kg of solvent

D. all of the above -- > FALSE since B and C are false

From the list

Choose A only