Question

5. Using your knowledge of intermolecular forces, explain the following observations: a. Rare gases and hydrogen assume liquid state at finite temperature. b. In the separation of aromatics from paraffins by extraction, liquid SO2 is a better solvent than liquid NHs. At 30°C, the solubilities of ethane and acetylene in n-octane are about the same. However, at the same temperature, the solubility of acetylene in c. dimethylformamide is very much larger than that of ethane. d. One of the main reasons for the differences in melting points of molten salts and room temperature ionic liquids is the asymmetry built into at least one of the ions of the former.

Answer 1

5.

(a) Under finite temperature and also some pressure, the hydrogen gas and rare gases will get compressed and due to which, they will convert their physical form from gaseous to liquid. The inter-molecular bonds will become stronger and the molecule will occupy less space.

(b) As we know that in chemistry substances which have same polar behavior dissolve easily. So as we already know that hydrocarbons are non-polar and as a result they will dissolve much easily and quickly in a solvent of SO₂(Non-polar) than NH₃(Polar).

(c) As we know that acetylene will have much dense electron cloud over it's compound due to triple bond, and due it the compound will be highly unstable than that of ethane. Due to this fact the reactivity of acetylene will be much higher than that of ethane when brought in contact with a solvent like DMF and thus it's solubility will be greater. Note that acetylene is highly unstable even at the room temperature conditions.

Reactivity (The willingness to react) is inversely proportional to the stability of compound.

(d)In Ionic salts the bonds are ionic. IT means that the transfer of ions take place which provides strength to the salt. Now molten salts at room temperature have at least one asymmetry built into one of the ions which disturbs the bond between the ions and make the bond weak. So as a result the bond is broken much easier than other ionic salts which allows it to meld at room temperature while other salts remain solid.