The vapor pressure of 1 M of KI solution is ________ 1 M of glucose solution. This is because vapor pressure depends only on the _________.
Which option correctly completes this statement?
the same as; concentration of the solute
less than; number of particles of solute
less than; molar mass of the solute
higher than; molar mass of the solute
C?
Here is a statement made to me 72 years ago by my freshman chemistry teacher. "When a non-volatile solute (KI and glucose are non-volatile solutes) is dissolved in a volatile solvent (water in this case), three things happen.
1. The freezing point is lowered.
2.The boiling point is raised.
3. The vapor pressure of the solvent is lowered.
The extent to which these three things happen depends SOLELY on the number of dissolved particles.
So 1 M solutions should have the same vapor pressure BUT KI dissociates into TWO particles while glucose does not.Since the KI solution has twice as many particles as the glucose solution then the KI soln will have a smaller vapor pressure.
Great post DrBob!
Yes, the correct option is C. The vapor pressure of 1 M KI solution is less than 1 M glucose solution. This is because vapor pressure depends only on the molar mass of the solute.
Yes, the correct option to complete the statement is "less than; number of particles of solute." The vapor pressure of a solution depends on the number of particles of solute present in the solution, regardless of their molar masses or concentrations.
To understand why the vapor pressure depends on the number of particles of solute, we need to consider Raoult's Law. According to Raoult's Law, the vapor pressure of an ideal solution is directly proportional to the mole fraction of the solvent in the solution.
In this case, comparing a 1 M KI solution to a 1 M glucose solution, we know that both solutions have the same concentration of solute (1 M). However, the number of particles of solute present in each solution is different.
In a 1 M KI solution, KI dissociates into one K+ ion and one I- ion. Therefore, each KI compound contributes two particles (one K+ ion and one I- ion) to the total number of particles in the solution.
On the other hand, a 1 M glucose solution does not dissociate into multiple particles. Each glucose molecule contributes only one particle.
Since the vapor pressure of a solution depends on the number of particles, the 1 M KI solution will have a lower vapor pressure compared to the 1 M glucose solution. Hence, the correct completion of the statement is "less than; number of particles of solute."