1. Tardigrade
  2. Question
  3. Chemistry
  4. A mixture of NH3(g) and N2H4(g) is placed in a sealed container at 300 K. The total pressure is 0.5 atm. The container is heated to 1200 K at which both substances decompose completely according to the equations 2NH3(g) arrow N2(g) + 3H2(g) and N2H4(g) arrow N2(g) + 2H2(g) After decomposition is complete, the total pressure at 1200 K is found to be 4.5 atm. Find the mole % of N2H4 in the original mixture.

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Q. A mixture of $NH_3(g)$ and $N_2H_4(g)$ is placed in a sealed container at $300 \,K$. The total pressure is $0.5$ atm. The container is heated to $1200\, K$ at which both substances decompose completely according to the equations
$2NH_3(g) \rightarrow N2(g) + 3H_2(g)$
and $N_2H_4(g) \rightarrow N_2(g) + 2H_2(g)$
After decomposition is complete, the total pressure at $1200 \,K$ is found to be $4.5$ atm. Find the mole $\%$ of $N_2H_4$ in the original mixture.

States of Matter

Solution:

Let initial mixture contains $n_1$ and $n_2$ moles of $NH_3$ and $N_2H_4$ respectively.
Total moles of gases originally present $= n_1 + n_2$
Total moles of gases after decomposition of gases
$= 2n_1 + 3n_2$
$0.5 \times V = (n_1 + n_2)R \times 300$
$4.5 \times V = (2n_1 + 3n_2) R \times 1200$
$\frac{2n_1 + 3n_2}{n_1 + n_2} = \frac{9}{4}$
$\frac{n_2}{n_1} = \frac{1}{3}$
$ \frac{n_2}{n_1 + n_2} \times 100 = 25\%$