To determine which of the given options would have the highest vapor pressure, we need to consider the effect of solutes on the vapor pressure of the solvent. This effect is explained by Raoult's Law, which states:
[tex]\[ P_{\text{solution}} = X_{\text{solvent}} \cdot P^0_{\text{solvent}} \][/tex]
Where:
- [tex]\( P_{\text{solution}} \)[/tex] is the vapor pressure of the solution.
- [tex]\( X_{\text{solvent}} \)[/tex] is the mole fraction of the solvent in the solution.
- [tex]\( P^0_{\text{solvent}} \)[/tex] is the vapor pressure of the pure solvent.
Adding a solute to a solvent lowers the vapor pressure of the solvent because the solvent's mole fraction decreases. The degree to which the vapor pressure is lowered depends on the number of particles the solute produces in solution.
### Analysis of Each Option:
1. Option A: 1.0 M solution of ionic compound sodium chloride (NaCl)
- Sodium chloride is an ionic compound and dissociates completely in water to form two ions: Na⁺ and Cl⁻.
- Therefore, a 1.0 M solution of NaCl will have an effective particle concentration of approximately 2.0 M.
2. Option B: 1.0 M solution of ionic compound potassium chloride (KCl)
- Potassium chloride, like sodium chloride, is an ionic compound and dissociates completely in water to form two ions: K⁺ and Cl⁻.
- Thus, a 1.0 M solution of KCl will also have an effective particle concentration of approximately 2.0 M.
3. Option C: 1.0 M solution of molecular compound sucrose (C₁₂H₂₂O₁₁)
- Sucrose is a molecular compound and does not dissociate into ions when dissolved in water. It remains as whole molecules.
- Hence, a 1.0 M solution of sucrose has a particle concentration of 1.0 M.
4. Option D: pure water
- Pure water has no solute particles present, so its vapor pressure is not lowered by the presence of solutes.
### Conclusion:
- Solutions A and B have higher particle concentrations due to dissociation into ions, leading to a greater lowering of the vapor pressure.
- Solution C has a lower particle concentration compared to solutions A and B, so its vapor pressure is higher but still lower than pure water.
- Pure water has the highest vapor pressure because it contains no solutes to lower the vapor pressure.
Thus, the correct answer is:
D. pure water
