**Observations and Questions**1. **Observation**: The enthalpy of vaporization of Substance A is smaller than that of Substance B. - **Question**: At any temperature where both substances are liquid, which has the higher vapor pressure? - Substance A - Substance B - Neither, A and B have the same vapor pressure. - It's impossible to know without more information.2. **Observation**: At 1 atm pressure, Substance E boils at –18 °C and Substance F boils at –32 °C. - **Question**: Which has a higher vapor pressure? - Substance E - Substance F - Neither, E and F have the same vapor pressure. - It's impossible to know without more information.3. **Observation**: At 68 °C, Substance C has a vapor pressure of 141 torr and Substance D has a vapor pressure of 101 torr. - **Question**: Which has a higher boiling point? - Substance C - Substance D - Neither, C and D have the same boiling point. - It's impossible to know without more information.

Few points we need to remember to solve this question,1. 2. 3. 4. Observation 1;Given that enthalpy of vaporization of A is smaller than B. That is A will vaporize first, thus more vapor will form from A than B at a given time. So as more vapor is present above the liquid, the higher the vapor pressure. So, vapor pressure of A will be higher.Observation 2;At a given pressure, E boils at -180C or 255 K and F boils at -320C or 241 K. That means F has less boiling point. So the bonds between F molecules must be weaker and more vapor can form at a given time. So as more vapor is forming the vapor pressure will also be higher. Thus F has higher vapor pressure..Observation 3;At a given temperature, C has vapor pressure 141 torr and D has vapor pressure 110 torr. That is vapor pressure of C is more. It means that the C can attain the external pressure easily. Since more vapor is forming, it starts to boil at lower temperature than D boil. So boiling point of C is less and boiling point of the D is higher. Answers;Observation 1- substance A has higher vapor pressureObservation 2- substance F has higher vapor pressureObservation 3-substance D has higher boiling point