Heavier compounds tend to have higher boiling points. However, sulphur dichloride (Mr= 103.1 gmol-1) and sulphur hexafluoride (Mr = 146.1 g mol-1) have the boiling point of 59 °C and -50.8 °C respectively. Explain this phenomenon.

there are two significant figures.

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.