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The equation used to calculate the change in freezing point (ΔTf) of a substance is:_______
ΔTf = Kfm
where Kf is the freezing point depression constant and m is the molality of the solution. Which of the statements explains why molality is used instead of molarity in this equation?
A. Molality does not appear in many equations, so it is used here to distinguish this equation from other similar ones.
B. As the temperature of a solution changes, its volume will also change, which will affect its molarity but not its molality.
C. In solutions, moles are not directly related to grams and the freezing point of a solution is dependent solely on the number of grams of solute.
D. The equation was originally published with m as a typo, rather than M, but the values are close enough that the equation is still valid.

Respuesta :

muhammadsaadhussain2

Answer:

B. As the temperature of a solution changes, its volume will also change, which will affect its molarity but not its molality.

Explanation:

Molality is given by the following equation:

[tex]Molality = \frac{moles of solute}{kg of solvent}[/tex]

While the molarity formula is given as

[tex]Molarity=\frac{moles of solute}{Lof solvent}[/tex]

The volume of solvent changes with temperature so it will be impractical to use molarity as it accounts for the volume of solution in its formula, which will create an error. Molality, on the other hand, uses Kg of solvent; which is not dependent on temperature. Hence, its value will not change  

B. As the temperature of a solution changes, its volume will also change, which will affect its molarity but not its molality.

The following information should be considered:

  • The volume of solvent changes with temperature thus it should be be impractical for using the molarity because it accounts for the volume of solution in its formula, that develops an error.
  • Molality, on the other hand, uses Kg of solvent; i.e. not dependent on temperature.

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