Some Chemistry questions I am struggling with...

Question

I would love to know how to find the condensation point, London Dispersion Forces and boiling point.

These are my questions:

1. Select which of the following hydrocarbons would exhibit a higher condensation point: Ethane or Butane
2. Select which of the following hydrocarbons would exhibit a higher boiling point: Ethane or Butane
3. Select which of the following hydrocarbons would exhibit stronger London Dispersion Forces: Ethane or Butane

Answer 1

1. higher condensation point: butane

2. higher boiling point: butane

3. stronger London Dispersion Forces: butane

Typically higher molecular weight means stronger London Dispersion Forces because either there are more atoms (as in butane over ethane) or more polarizable, heavier atoms contributing to the force.

The stronger the London Dispersion Forces, the higher the boiling point and condensation point, because it takes more thermal energy to separate the molecules from each other (to convert the liquid phase to the gas phase).

I think condensation point and boiling point are about conversions between the same two states (gas and liquid) just in the opposite direction. From water the condensation point and boiling point are both the same temperature: 100 °C (at atmospheric pressure).