Explain the differences in the boiling temperatures of the following compounds. hcl-85 degrees celsius, hf 20 degrees celsius, ticl4 136 degrees degrees, cscl 1290 degrees celsius, and licl 1360 degrees celsius

The electronegativity difference between the two atoms determines what type of bond is formed, and how strong that bond is. Boiling points are effected by various factors such as intermolecular attraction, molecular weight, and branching (in organic compounds). 

The H-Cl bond has the least difference in electroneg. of the entire series, thus the bond is the least polarized and the intermolecular forces are the weakest. Fluoride is a hard anion, it holds onto its electrons the strongest, and has a small size. It is also the most electronegative of all the elements so the electroneg. diff. is greater than in H-Cl bond, so the H-F polar covalent bond is more polarized and the intermolecular attraction will be stronger and require more energy to vaporize and overcome atmospheric pressure. 

The electronegativity of Ti is less than H, (1.5 as compared to 2.1), so the Ti-Cl bonds are probably more polarized, the compound has a much higher molecular weight the previous gas and liquid, and it is a crystalline solid so there is a lattice energy that must be overcome before it can be melted and subsequently boiled. 

CsCl is an ionic compound and has a crystal structure. Because of the greater electronegativity diff. there is the transfer of valance electrons so that each ion has a full outer shell. The charges on the ions make ionic bonds very strong and require a large amount of energy to overcome. Even though Cs is more electropositive than Li, Li is a much smaller cation allowing closer packing in the crystal structure. The distance between the charges are minimized, thereby making the ion pair more difficult to separate. That is why LiCl has a higher boiling point, even though the electronegativity difference in CsCl is marginally greater.