1. At 1 atm and 298 k, pentane is a liquid whereas propane is a gas. Explain.
2. At 1 atm and 298 k, methanol is a liquid whereas propane is a gas. Explain.
3. Indicate the hybridization of the carbon atom in each of the following:
i) Methanol
ii) Methanoic (formic) acid
4. Draw the complete lewis electron-dot diagram for a molecule of propanoic acid, HC3H5O2.
5. Explain the following observations about the two carbon-oxygen bonds in the methanoate (formate) anion, HCO2-.
i) The two carbon-oxygen bonds in the methanoate (formate) anion, HCO2-, have the same length.
ii)The length of the carbon-oxygen bonds in the methanoate (formate) anion, HCO2-, is the intermediate between the length of the carbon-oxygen bond in methanol and the length of the carbon-oxygen bond in methanal.

1. There are stronger inter-molecular forces at play when a certain substance is a liquid as compared to a gas. Pentane is liquid due to the hydrogen bonding present between its molecules.

2. Inter-molecular forces between propane molecules are weaker as compared to methanol. There are no hydrogen bonds present between the propane molecules.

3. Methanol:

Methanoic (formic) acid:

4. attached

5. i) Since there are two resonance structures possible in this case, the bond length is given as an average value of the carbon-oxygen bond, one where it is a single bond and the other where its a double bond.

ii) Continuing from the explanation above, the value of bond length in the case of methanoate anion would be in between the bond length of a single carbon-oxygen bond and a double carbon-oxygen bond in methanol.

Hope that answers the questions, have a great day!