Question

Which of the following aqueous solutions will have the lowest vapor pressure at 25 degrees Celsius? (2 points)

1.0 M Fe(NO3)3
1.0 M C6H12O6
1.0 M KNO3
1.0 M CaCl2

Answer 1

Solution 1.0 M Fe(NO3)3

Step-by-step explanation:

-Vapor pressure is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system.

- There is an inverse relation between vapor pressure and the number of particles in the solution.

- Since the four solutions are of equal concentration, the one with the lowest vapor pressure is that which gives greatest number of particles in its solution.

- Sol (1), produces 4 moles of ions per mole of substance. Fe(NO3)3 → Fe^3+ + 3 NO3^-

- Sol (2), produces 1 moles of ions per mole of substance because C2H12O6 is a non-electrolyte.

- Sol (3), produces 2 moles of ions per mole of substance. KNO3 → K^+ + NO3^-

- Sol (4), produces 3 moles of ions per mole of substance. CaCl2 → Ca^2+ + 2Cl^-

So the substance that has the lowest vapor pressure is Fe(NO3)3..