When a solute such as potassium chloride (KCl) is dissolved in a solvent like water (H2O), it affects the colligative properties of the solvent. These properties are dependent on the number of solute particles in solution and are independent of the chemical identity of the solute particles. The colligative properties include boiling point elevation and freezing point depression.
**Boiling Point Elevation:**
Boiling point elevation occurs because the introduction of solute particles into the solvent increases the boiling point of the solvent. This happens because the presence of solute particles disrupts the ability of the solvent molecules to escape the liquid phase and enter the gas phase. To achieve boiling, the system now requires a higher temperature to allow the solvent molecules to have enough energy to overcome the presence of the solute and transition into the gas phase.
**Freezing Point Depression:**
Similarly, the freezing point of the solution is lowered in the presence of a solute. This is because the solute particles interfere with the formation of the organized structure of a solid. Solvent molecules are less likely to come together and crystallize at the original freezing temperature because the solute gets in the way, thus a lower temperature is required to solidify the solvent, so the freezing point decreases.
In summary, when you dissolve 1 mole of KCl in 1000 grams of water:
- The boiling point of the solution will be higher than that of pure water.
- The freezing point of the solution will be lower than that of pure water.
Therefore, the correct answer to the question is:
c. both the boiling point and the freezing point of the H₂O
This is an expected result based on the principles of colligative properties, as both the processes of boiling and freezing are influenced by the presence of a non-volatile solute.
