If one mole of each is dissolved in 1.00 L of water, which will lower the vapor pressure the most? Why?

A)C12H22O11
B)C3H7OH
C)NaNO3
D)MgCl

1 answer

delta T = i*Kf*m
So you want the highest delta T.
i is the van't hoff factor, Kf is constant, molality is constant in this case so it appears to depend upon i.
i = 1 for A
i = 1 for B
i = 2 for C
i = 2 for what you have but I suspect you made a typo and that should be MgCl2 for which i = 3.