The boiling point of cis-1,2-dichloethene is higher than that of tis trans-isomer-why?

S-I: The boiling point of cis-1,2-dichloroethene is higher than corresponding trans-isomer. S-II: The dipole moment of cis-1,2-dichloroethene is higher than trans isomer.

Why the boiling point of salt water is higher than pure water?

Why the boiling point of HF is higher than that of other hydrogen halides?

Why the boiling point of ethyl alcohol is higher than diethyl ether?

Why is the boiling point of a solution always higher than that of a pure solvent ?