Question

If all the amines are represented by the formula $R-{NH}_2$, the value of R in all the amines is:

• A. $C_3{H}_7-$
• B. $C_4{H}_9-$
• C. $C_5{H}_{11}-$
• D. $C_2{H}_5-$

Answer 1

Answer: (B)

$C_4{H}_9-$

R.E.F image

Let the formula of amines be $RN{H}_2$ and that of the

hydrochloride be $R\stackrel{\oplus }{N}{H}_3\stackrel{\oplus }{C}I$.

Let the weight of $R\stackrel{\oplus }{N}{H}_3\stackrel{\oplus }{C}I$ be $x$ gm

$\therefore x$ gm of $R\stackrel{\oplus }{N}{H}_3\stackrel{\oplus }{C}I$ contains $\Rightarrow 35$ gm of $Cl$

$100$ gm of $R\stackrel{\oplus }{N}{H}_3\stackrel{\oplus }{C}I\Rightarrow \frac{35.5}{x}\times 100=32.42$

$\therefore x=109.5$ $\therefore R\stackrel{\oplus }{N}{H}_3\stackrel{\oplus }{Cl}=109.5$

Let the weight of $R=y$

$\therefore y+17+35.5=109.5$

$y=57;R$ can be $C_4{H}_9$

Formula is $C_4{H}_9\stackrel{\oplus }{N}{H}_{3}C{l}^{-\ominus }$.