Question

Phosphorous and chlorine gases combine to produce phosphorous trichloride:

P₂ (g) + 3Cl₂ (g) → 2PCl₃ (g)

ΔG° at 298 K for this reaction is -642,900 J/mol. The value of ΔG at 298 K for a reaction mixture that consists of    and  is __________.

		-7.28 × 103 kJ/mol
		-3.88 × 103 kJ/mol
		-649.5 kJ/mol
		-708.4 kJ/mol
		-44.2 kJ/mol

Thank you!

Answer 1

The question is incomplete. The partial pressure must be provided.

I am giving some values for partial pressure of each gas -

Partial pressure of 1.5 atm P2, 1.6 atm Cl2, and 0.65 atm PCl3.

As the equilibrium is not established, we need to find out reaction quotient, Q

Q = (pPCl3)² / [ (pP2) × (pCl2)³] = (0.65)²/[1.5 × (1.6)³ ​​​​​​]= 0.068766273

T = 298 K

R = 8.314 J/K.mol

ΔG° = -642,900 J/mol.

The formula used is -

∆G = ∆G° + RTlnQ ....(1)

Let's calculate RTlnQ at first

= 8.314 J/K.mol × 298 K × ln (0.068766276)

= -6632.563876 J/mol ....(2)

Putting this value in (1) -

∆G = -642900 + (-6632.563876) J/mol

∆G = -649532.5639 J/mol

∆G = -649.5 kJ/mol

** This values are from a known problem, if you have different values of partial pressure comment below, I will solve it. Or you can solve it by using the above method. Don't give dislike.