Choose a substance with the highest vapor pressure. So highest vapor pressure translates to the weakest intermolecular force. So if we take a look here we have silver perchlorate in methanol. So this is an ionic compound within a substance that has hydrogen bonding. So that means it's polar. So this would be ion dipole.
Next we have is a nonmetal by itself, so we have Krypton, so it's a nonmetal by itself. So it's nonpolar. So it's going to be London dispersion forces. For the next one, we have a hydrocarbon which is nonpolar as well, so it would be also London dispersion forces.
And then finally we have hydrogen with sulfur. We're going to say here hydrogen with sulfur. If you were to draw this out, you'd have sulfur with lone pairs. And remember, if your central element has lone pairs, it is not a perfect shape and by default it is polar. So we're dealing with a polar covalent compound. So this is dipole dipole.
Highest vapor pressure will belong to the weakest intermolecular force, which would be London dispersion. So here we're comparing Krypton to chapter 4, which is methane. Remember to compare their strengths we look at their overall mass. Krypton weighs approximately 83.80g, and if you added up the one carbon in the four hydrogens of methane, it'd be about 16 grams.
Since Krypton weighs more, it's stronger in terms of London dispersion forces, but remember we're looking for the weakest 1. The weakest one would translate to the highest framework pressure. Since methane weighs less, it is weaker and therefore would have the highest vapor pressure. So here the answer would be option C.
