Question

In the synthesis of ammonia from nitrogen and hydrogen gases, if $ 6\times 10^{-2} $ moles of hydrogen disappears in $10\,$ minutes, the number of moles of ammonia formed in $3\,$ minutes is

• A. $ 1.8\times 10^{-2} $
• B. $ 1.2\times {{10}^{-2}} $
• C. $ 4.0\times {{10}^{-2}} $
• D. $ 3.6\times {{10}^{-2}} $

Answer 1

Answer: (B)

$\because$ In $10$ min, the number of $H _{2}$ disappears $=6 \times 10^{-2}$
$\therefore $ In $3$ min, the number of moles of $H _{2}$
disappears $=\frac{6 \times 10^{-2} \times 3}{10}$
$=1.8 \times 10^{-2}$
$N_{2}+3 H_{2} \rightleftharpoons 2 N H_{3}$
$\Rightarrow \frac{1}{3}\left[\right.$ Rate of disappearance of $\left.H _{2}\right]$
$=\frac{1}{2}\left[\right.$ Rate of formation of $\left.NH _{3}\right]$
$\therefore $ Rate of formation of $N H_{3}=\frac{2}{3} \times 1.8 \times 10^{-2}$
$=1.2 \times 10^{-2}$ mol $NH _{3}$
$\therefore 1.2 \times 10^{-2}$ moles of $NH _{3}$ are formed.