Deduction of the compound's structure:

• The carbonyl compound $\text{C}_3\text{H}_6\text{O}$ could be either propanal (an aldehyde) or acetone / propan-2-one (a ketone).
• Because it does not reduce Tollens' reagent, it is not an aldehyde; hence it must be acetone ($\text{CH}_3\text{COCH}_3$).
• Acetone contains the carbonyl group ($\gt \text{C=O}$), so it reacts with hydroxylamine to form an oxime: $(\text{CH}_3)_2\text{C=N-OH}$.
• Acetone possesses a methyl ketone group ($\text{CH}_3\text{CO}-$), so when treated with iodine and aqueous sodium hydroxide, it undergoes the iodoform reaction to form a yellow precipitate of iodoform ($\text{CHI}_3$).

In the gaseous phase, there is no solvation effect or steric hindrance due to hydration. The basic character of amines is determined solely by the electron-donating inductive effect ($+I$ effect) of alkyl groups. The greater the number of methyl groups, the higher the electron density on nitrogen and the more readily it accepts a proton:

$$3^\circ\text{ amine} \gt 2^\circ\text{ amine} \gt 1^\circ\text{ amine} \gt \text{NH}_3$$ $$(\text{CH}_3)_3\text{N} \gt (\text{CH}_3)_2\text{NH} \gt \text{CH}_3\text{NH}_2 \gt \text{NH}_3$$

Ethylamine ($\text{C}_2\text{H}_5\text{NH}_2$) is a primary amine containing a basic lone pair of electrons on nitrogen. When it reacts with one mole of hydrochloric acid ($\text{HCl}$), nitrogen donates its lone pair to a proton ($\text{H}^+$), forming ethylammonium chloride:

$$\text{C}_2\text{H}_5\text{NH}_2 + \text{HCl} \rightarrow \text{C}_2\text{H}_5\text{NH}_3^+\text{Cl}^-$$