A gas mixture of 20 moles nitrogen and 70 moles hydrogen is fed to a reactor in which ammonia is produced. Assuming that the reaction proceeds to completion, determine the composition of the exit gas stream both in mole and mass %. If 75% of nitrogen gets converted, what will be the corresponding fractions?

Respuesta :

Answer:

Complete reaction

mole %: 0% N₂; 20% H₂; 80% NH₃

Gram %: 0% N₂; 2,9% H₂; 97,1% NH₃

75% reaction:

mole%: 8,3% N₂; 41,7% H₂; 50% NH₃

Gram: 20% N₂; 7,2% H₂; 72,8% NH₃

Explanation:

The global reaction in the reactor is:

N₂(g) + 3 H₂ (g) → 2 NH₃ (g)

For a complete reaction of 20 moles of N₂(g) you need:

20 moles N₂ ₓ [tex]\frac{3 mol H_2}{1 mol N_2}[/tex] = 60 moles of H₂(g)

So, 10 moles of H₂(g) will stay in the end.

The moles produced of NH₃ are:

20 moles N₂ ₓ [tex]\frac{2 mol NH_3}{1 mol N_2}[/tex] = 40 moles of NH₃(g)

Thus, the final composition in moles is:

0 moles N₂; 10 moles H₂; 40 moles of NH₃

The mole % is:

0% N₂; ¹⁰/₅₀ ₓ 100 = 20% H₂; ⁴⁰/₅₀ ₓ100 = 80% NH₃

In grams you have:

10 moles H₂ [tex]\frac{2,02 g}{1 mol}[/tex] = 20,2 g of H₂

40 moles NH₃ [tex]\frac{17,03 g}{1 mol}[/tex] = 681,2 g of NH₃

0% N₂; [tex]\frac{20,2 g}{701,4}[/tex] ₓ 100 = 2,9% H₂; [tex]\frac{681,2 g}{701,4}[/tex] ₓ100 = 97,1% NH₃

With a 75% of conversion you have that the moles produced of NH₃ are:

40 moles of NH₃(g) × 75% = 30 moles of NH₃

The necessary moles to produce these moles of NH₃ are:

30 moles NH₃ ₓ [tex]\frac{3 mol H_2}{2 mol NH_3}[/tex] = 45 moles of H₂(g)

So, 25 moles of H₂(g) will stay in the end.

30 moles NH₃ ₓ [tex]\frac{1 mol N_2}{2 mol NH_3}[/tex] = 15 moles of N₂(g)

So, 5 moles of H₂(g) will stay in the end.

Thus, the final composition in moles is:

5 moles N₂; 25 moles H₂; 30 moles of NH₃

The mole % is:

⁵/₆₀ ₓ 100 =8,3% N₂; ²⁵/₆₀ ₓ 100 = 41,7% H₂; ³⁰/₆₀ ₓ100 = 50% NH₃

In grams you have:

5 moles N₂ [tex]\frac{28 g}{1 mol}[/tex] = 140 g of N₂

25 moles H₂ [tex]\frac{2,02 g}{1 mol}[/tex] = 50,5 g of H₂

30 moles NH₃ [tex]\frac{17,03 g}{1 mol}[/tex] = 510,9 g of NH₃

[tex]\frac{140 g}{701,4}[/tex] ₓ 100 =20% N₂; [tex]\frac{ 50,5g}{701,4}[/tex] ₓ 100 = 7,2% H₂; [tex]\frac{510,9 g}{701,4}[/tex] ₓ100 = 72,8% NH₃

I hope it helps!