When NaCl is added to aqueous solution of glucose

Options

A. Freezing point is lowered
B. Freezing point is raised
C. Freezing point does not change
D. Variation is freezing point can't be predicted

Answer

**Step-by-Step Solution:**

1. **Understanding the Components:**
- We have an aqueous solution of glucose, which is a non-volatile, non-electrolyte solute.
- When NaCl (sodium chloride) is added to this solution, it dissociates into its ions (Na⁺ and Cl⁻) in the solution.

2. **Effect of Glucose on Freezing Point:**
- The addition of glucose to pure water lowers the freezing point of the solution. This phenomenon is known as freezing point depression.
- The vapor pressure of the solution (Ps) is lower than that of pure water (P0) due to the presence of glucose molecules, which disrupt the formation of ice.

3. **Graphical Representation:**
- A graph of vapor pressure vs. temperature shows that as the temperature decreases, the vapor pressure of the solution also decreases.
- The freezing point of the solution is the temperature at which the vapor pressure of the solid and liquid phases are equal.

4. **Adding NaCl to the Solution:**
- When NaCl is added to the glucose solution, it dissociates into Na⁺ and Cl⁻ ions, effectively increasing the number of solute particles in the solution.
- This increase in solute particles leads to a further decrease in the vapor pressure (Ps) of the solution.

5. **Impact on Freezing Point:**
- The presence of additional solute particles (from NaCl) means that the freezing point of the solution will be lowered even more than it was with glucose alone.
- The new freezing point can be represented as a further depression (ΔTf) from the original freezing point of the glucose solution.

6. **Conclusion:**
- Therefore, when NaCl is added to an aqueous solution of glucose, the freezing point of the solution is lowered due to the combined effect of glucose and the dissociated ions from NaCl.

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