Which of the following will have the lowest vapor pressure?
Practice Questions
Q1
Which of the following will have the lowest vapor pressure?
Pure solvent
0.1 M NaCl
0.1 M KCl
0.1 M CaCl2
Questions & Step-by-Step Solutions
Which of the following will have the lowest vapor pressure?
Correct Answer: 0.1 M CaCl2
Step 1: Understand what vapor pressure is. Vapor pressure is the pressure of a vapor in contact with its liquid or solid form. It indicates how easily a substance can evaporate.
Step 2: Know that when a solute is added to a solvent, the vapor pressure of the solvent decreases. This is called vapor pressure lowering.
Step 3: Recognize that the more particles a solute produces in solution, the greater the effect on lowering the vapor pressure.
Step 4: Identify the solute in the question. 0.1 M CaCl2 dissociates into 3 ions: 1 calcium ion (Ca²⁺) and 2 chloride ions (Cl⁻).
Step 5: Compare the number of particles produced by different solutes. Since CaCl2 produces 3 particles, it will lower the vapor pressure more than solutes that produce fewer particles.
Step 6: Conclude that 0.1 M CaCl2 will have the lowest vapor pressure because it produces the most particles in solution.
