Investigating changes in colligative properties involves the measurement of a solution’s concentration in molality instead of molarity because of which of the following?
the mass of the solvent does not change, but its volume does change, as temperature changes.
the volume of a solution can be measured more accurately than the mass of a solution.
the volume of a solution does not change, but its mass does change, as temperature changes.
the mass of a solvent can be measured more accurately than the volume of a solvent.
The first and last statements are true.
To answer this question, we need to understand the difference between molarity and molality, as well as the concept of colligative properties.
Molarity (M) is a measurement of the concentration of a solute in a solution, expressed as the number of moles of solute per liter of solution. It is commonly used when the volume of the solution is the relevant factor.
Molality (m) is a measurement of the concentration of a solute in a solution, expressed as the number of moles of solute per kilogram of solvent. It is used when the mass of the solvent is the relevant factor.
Colligative properties are properties of solutions that depend on the concentration of solute particles, rather than the identity of the solute itself. Examples of colligative properties include boiling point elevation and freezing point depression.
Now, let's consider the options:
1. the mass of the solvent does not change, but its volume does change, as temperature changes.
This option is true, but it does not explain why molality is used instead of molarity for investigating changes in colligative properties.
2. the volume of a solution can be measured more accurately than the mass of a solution.
This option is false. The accuracy of measurement depends on the specific tools and techniques used, and both mass and volume can be measured accurately.
3. the volume of a solution does not change, but its mass does change, as temperature changes.
This option is also true, but it does not explain why molality is used instead of molarity for investigating changes in colligative properties.
4. the mass of a solvent can be measured more accurately than the volume of a solvent.
This option is the correct answer. The choice to use molality over molarity is because it is generally easier and more accurate to measure the mass of a solvent than its volume. Measuring volume accurately can be more challenging, especially in cases where the temperature changes and the volume expands or contracts.
Therefore, the correct answer is option 4: "the mass of a solvent can be measured more accurately than the volume of a solvent."