An organic compound having molecular formula $C_2H_6O$ undergoes oxidation with $K_2Cr_2O_7 / H_2SO_4$ to produce $X$ which contains $40\,\%$ carbon,$6.7\,\%$ hydrogen and $53.3\,\%$ oxygen. The molecular formula of the compound $X$ is

Product $(A)$ and $(B)$ respectively in the above reaction are

What are $X$ and $Y$ respectively in the following reactions?

The product $(X)$ of the reaction is:

Draw the structures of the following compounds:
$(i)$ $3-$Methylbutanal
$(ii)$ $p-$Nitropropiophenone
$(iii)$ $p-$Methylbenzaldehyde
$(iv)$ $4-$Methylpent$-3-$en$-2-$one
$(v)$ $4-$Chloropentan$-2-$one
$(vi)$ $3-$Bromo$-4-$phenylpentanoic acid
$(vii)$ $p, p^{\prime}-$Dihydroxybenzophenone
$(viii)$ Hex$-2-$en$-4-$ynoic acid

The increasing order of the acidity of the following carboxylic acids is: