30.4k views
3 votes
Be sure to answer all parts. ΔG o for the reaction H2(g) + I2(g) ⇌ 2HI(g) is 2.60 kJ/mol at 25°C. Calculate ΔG, and predict the direction in which the reaction is spontaneous. The initial pressures are: PH2 = 3.10 atm PI2 = 1.5 atm PHI = 1.75 atm

ΔG =
a. the reaction is spontaneous in the forward direction
b. the reaction is spontaneous in the reverse direction
c. cannot be determined

User KarelZe
by
9.3k points

1 Answer

4 votes

Answer:

∆G = 1.567 kJ/mole

The reaction is nonspontaneous., or will be spontaneous in the reverse direction

Step-by-step explanation:

Step 1: The balanced equation

H2(g) + I2(g) ⇌ 2HI(g) 2.60 kJ/mol at 25°C.

Step 2: Data given

The initial pressures are:

pH2 = 3.10 atm

pI2 = 1.5 atm

pHI = 1.75 atm

Step 3: Calculate Q

Kp = (pHI)^2 / (pH2)(pI2)

Q has the same form but we substitute the non-equilibrium values given in the problem.

Q = (1.75)² / (3.10*1.5) = 0.659

Step 4: Calculate gibbs free energy

∆G = ∆G˚ + RTlnQ = 2600 J/mole + (8.31 J/mole K)(298 K)(ln 0.659) = 2600 J/mole - 1032.729 J/mole

= 1567.271‬ J/mole = 1.567 kJ/mole

Interpret ∆G:

∆G > 0 the reaction is nonspontaneous., or will be spontaneous in the reverse direction

∆G < 0 the reaction is spontaneous.

If ∆G = 0 the reaction is essentially at equilibrium.

∆G = 1.567 kJ/mole

The reaction is nonspontaneous., or will be spontaneous in the reverse direction

User Homan
by
8.1k points
Welcome to QAmmunity.org, where you can ask questions and receive answers from other members of our community.