Question

Acetylene, C2H2, can be converted to ethane, C2H6, by a process known as hydrogenation. The reaction is C2H2(g) + 2H2(g) ⇌ C2H6(g) and it has ΔG∘ = -241.2 kJ/mol at 25∘C. What is the free energy change in kilojoules for the reaction under the following conditions at 25∘C? Substance Pressure C2H2(g) 8.58 H2(g) 3.06 C2H6(g) 0.261

Answer 1

-255.4 kJ

Step-by-step explanation:

The free energy of a reversible reaction can be calculated by:

ΔG = (ΔG° + RTlnQ)*n

Where R is the gas constant (8.314x10⁻³ kJ/mol.K), T is the temperature in K, n is the number of moles of the products (n =1), and Q is the reaction quotient, which is calculated based on the multiplication of partial pressures by the partial pressure of the products elevated by their coefficient divide by the multiplication of the partial pressure of the reactants elevated by their coefficients.

C₂H₂(g) + 2H₂(g) ⇄ C₂H₆(g)

Q = pC₂H₆/[pC₂H₂ * (pH₂)²]

Q = 0.261/[8.58*(3.06)²]

Q = 3.2487x10⁻³

ΔG = -241.2 + 8.314x10⁻³x298*ln(3.2487x10⁻³)

ΔG = -255.4 kJ