Question

The following liquids have about the same molar mass. The vapor pressure of each was measured in the open-ended manometer shown below, in which the height of the mercury is measured. Arrange the liquids in order of decreasing height of the mercury column, designated as h in the image. 1 = largest height: 4 = smallest height [Select] CH3CHCH2CH3 CH3 [Select ] CH2CH2CH2CH2CH2 [Select] CH3CH2CH2CH2OH [Select] CH2CH2CHOCHZ

Answer 1

Greater height of mercury means greater vapour pressure.

Vapour pressure is greater for the molecule with weaker intermolecular forces.

Option 1 is non polar.

It will have dispersion forces.

Due to more branching dispersion forces are weaker than option 2

Option 2 is non polar.

It will have dispersion forces. But stronger than option 1

Option 3 can form hydrogen bond because it has hydrogen attached to oxygen.

So, intermolecular forces are strongest here.

Option 4 is polar.

It can have dipole-dipole interaction,

So, intermolecular forces are 2nd strongest here.

So, option 1 will have highest vapour pressure and hence largest height.

Option 3 will have lowest height

Answer:

1

2

4

3