Question

In which one of the following equilibria $Δn_g$ value is zero?

• A. $2NOCI(g) ⇌ 2NO(g) + Cl_2(g)$
• B. $H_2(g)+Br_2(g)⇌ 2HBr(g)$
• C. $CO_2(g) + C(s) ⇌ 2CO(g)$
• D. $Ni(s)+4CO(g) ⇌ Ni(CO)_4 (g)$
• E. $N_2O_4(g) ⇌ 2NO_2(g)$

Answer 1

The Correct Option is B

We need to find the equilibrium where the change in the number of moles of gases (Δn_g) is zero.

Let's check each option:

• 1) \( 2NOCl(g) ⇌ 2NO(g) + Cl_2(g) \)
  Reactants = 2 mol, Products = 2 + 1 = 3 mol ⇒ Δn_g = 3 - 2 = 1
• 2) \( H_2(g) + Br_2(g) ⇌ 2HBr(g) \)
  Reactants = 1 + 1 = 2 mol, Products = 2 mol ⇒ Δn_g = 2 - 2 = 0 ✅
• 3) \( CO_2(g) + C(s) ⇌ 2CO(g) \)
  Reactants = 1 mol, Products = 2 mol ⇒ Δn_g = 2 - 1 = 1
• 4) \( Ni(s) + 4CO(g) ⇌ Ni(CO)_4(g) \)
  Solids are not counted ⇒ Reactants = 4 mol, Products = 1 mol ⇒ Δn_g = 1 - 4 = -3
• 5) \( N_2O_4(g) ⇌ 2NO_2(g) \)
  Reactants = 1 mol, Products = 2 mol ⇒ Δn_g = 2 - 1 = 1

Correct Answer:

2) \( H_2(g) + Br_2(g) ⇌ 2HBr(g) \) (Δn_g = 0)