Which of the following is NOT true of colligative properties? Colligative properties are...
A. responsible for lowering the vapor pressure of a solution versus the vapor pressure of the pure solvent.
B. independent of the chemical identity of the solute.
C. dependent on the mass of solute present.
D. dependent on the molar mass of the solute.
E. all of these are true.
http://en.wikipedia.org/wiki/Colligative_properties
To determine which statement is NOT true of colligative properties, we need to understand what colligative properties are.
Colligative properties are physical properties of a solution that depend on the number of solute particles present, regardless of their chemical identity. These properties include lowering the vapor pressure, raising the boiling point, lowering the freezing point, and increasing the osmotic pressure of the solvent.
Now, let's assess each statement:
A. Colligative properties are responsible for lowering the vapor pressure of a solution versus the vapor pressure of the pure solvent. This statement is true. Adding a non-volatile solute to a solvent lowers the vapor pressure due to the increase in the number of solute particles.
B. Colligative properties are independent of the chemical identity of the solute. This statement is true. Colligative properties depend on the number of solute particles and not their specific properties.
C. Colligative properties are dependent on the mass of solute present. This statement is true. Colligative properties are directly proportional to the number of solute particles present in the solution, which can be determined by the mass of the solute.
D. Colligative properties are dependent on the molar mass of the solute. This statement is NOT true. Colligative properties depend on the number of solute particles and not their molar mass. Therefore, this statement is the correct answer.
E. The statement "all of these are true" is not valid since we have identified one statement that is not true.
In conclusion, the statement that is NOT true of colligative properties is D, as colligative properties are not dependent on the molar mass of the solute.