Question

An unknown compound (A) has molecular formula $C_4{H}_6$. When (A) is treated with excess of $B{r}_2$, a new compound (B) with molecular formula $C_4{H}_{6}B{r}_4$ is formed. (A) forms a white precipitate with ammonical silver nitrate solution. Molar mass of (A) in ${\text{g mol}}^{-1}$ is $x$ and position of multiple bond is $y$. Find the value of $x/y$.

Answer 1

Given, molecular formula is $C_4{H}_6$. It must be an alkyne.
From the information given, (A) is a terminal alkyne as it gives positive test with tollen's reagent.
So, the compound (A) is but-1-yne.
Molar mass of (A), $x=12\times 4+6\times 1=54{\text{g mol}}^{-1}$
Position of multiple bond is $1$ i.e., $y=1$
$\therefore x/y=54$.