Amixture of nitrogen and hydrogen gases, at a temperature of 500

k, was put into an evacuated

vessel of volume 6.0

dm3. the vessel was then sealed.

n2(g) + 3h2(g) 2nh3(g)

the mixture was allowed to reach equilibrium. it was found that 7.2

mol of n2 and 12.0

mol of h2 were present in the equilibrium mixture. the value of the equilibrium constant, kc, for this equilibrium is 6.0 × 10–2 at 500

k.

what is the concentration of ammonia present in the equilibrium mixture at 500

k?

answer is b, i don't know why.

0.7589 mol/L ≅ 0.76 mol/L.

Explanation:

N₂(g) + 3H₂(g) ⇄ 2NH₃(g),

Kc = [NH₃]²/[N₂][H₂]³

Kc = 6.0 x 10⁻²,

[N₂] = (7.2 mol)/(6.0 L) = 1.2 mol/L, [H₂] = (12.0 mol)/(6.0 L) = 2.0 mol/L.

∴ [NH₃]² = (Kc)[N₂][H₂]³ = (6.0 x 10⁻²)(1.2 mol/L)(2.0 mol/L)³ = 0.576.

∴ [NH₃] = √(0.576) = 0.7589 mol/L ≅ 0.76 mol/L.

the electronic configuration of an atom with eight electrons is 1s²2s²2p⁴. the orbital diagrams are shown in the figure.

as per the hunds rule:

1. electrons tend to avoid being in the same orbital as per as practicable.

2. electrons in different orbitals of the same energy will have their spin parallel.

this can be illustrated from the multiplicity of the orbitals of the atom. as there are four electrons in the p orbital and p orbital has 3 sub-shells. the electrons can be fed in different ways as shown in the figure but the correct orbital diagram will be as per the hunds rule.