which of the following Has lowest Vapour Pressure at room temperature?

Question

1) CH4
2) CH3CL
3) CH2CL
4) CHCL3
5) CCL4

Answer 1

Boiling Points:

CH4 = 111.55 K
CH3Cl = 249 K
CH2Cl2 = 312.8 K
CHCl3 = 334.2 K
CCl4 = 350 K

The molecule with the highest molecular mass will have the lowest vapor pressure. I don't have a access to vapor pressure at room temperature, but the above boiling points reflect vapor pressures, so the one with the highest boiling point, CCl4, has the lowest vapor pressure.

Answer 2

CHCl3 has a dipole moment,but CCl4 has stronger van der \Waals forces. So with opposing theoretical effects, I don't think you can predict; you need to look at the data.

Almost certainly the one with highest boiling point.