Which of the following would have the highest vapor pressure?

a.

1.0 m solution of ionic compound sodium chloride (nacl)

b.

1.0 m solution of ionic compound potassium chloride (kcl)

c.

1.0 m solution of molecular compound sucrose (c12h22o11)

d.

pure water

Answer : The correct options is, (D) Pure water.

Explanation :

According to the relative lowering of vapor pressure, the vapor pressure of a component at a given temperature is equal to the mole fraction of that component of the solution multiplied by the vapor pressure of that component in the pure state.

Formula used :

where,

= vapor pressure of the pure component (water)

= vapor pressure of the solution  

= mole fraction of solute

i = Van't Hoff factor

(A) The dissociation of 0.1 M will be,

So, Van't Hoff factor = Number of solute particles = = 1 + 1 = 2

(B) The dissociation of 0.1 M will be,

So, Van't Hoff factor = Number of solute particles = = 1 + 1 = 2

(C) , sucrose is a non-electrolyte solute that means they retain their molecularity, and not undergo association or dissociation.

So, Van't Hoff factor = 1

(D) Pure water : As we know that the vapor pressure of a pure solvent is always greater than the vapor pressure of a solution that containing a non-volatile liquid.

As we know that the vapor pressure is depend on the Van't Hoff factor but the vapor pressure of a pure solvent is always greater.

Hence, from this we conclude that, the pure water have the highest vapor pressure.

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