Indicate whether ΔG increases, decreases, or does not change when the partial pressure of H₂ is increased in each of the following reactions: (a) N₂(g) + 3 H₂(g) ⇌ 2 NH₃(g) (b) 2 HBr(g) ⇌ H₂(g) + Br₂(g) (c) 2 H₂(g) + C₂H₂(g) ⇌ C₂H₆(g)

Verified step by step guidance

1. Step 1: Understand the relationship between Gibbs free energy (ΔG) and reaction quotient (Q). ΔG is related to the reaction quotient Q and the equilibrium constant K by the equation ΔG = ΔG° + RT ln(Q), where ΔG° is the standard Gibbs free energy change, R is the gas constant, and T is the temperature in Kelvin.
2. Step 2: Determine how the reaction quotient Q changes with an increase in the partial pressure of H₂. The reaction quotient Q is defined as the ratio of the products' partial pressures to the reactants' partial pressures, each raised to the power of their stoichiometric coefficients.
3. Step 3: Analyze reaction (a) N₂(g) + 3 H₂(g) ⇌ 2 NH₃(g). Increasing the partial pressure of H₂ will increase the denominator of Q, thus decreasing Q. Since Q < K, the reaction will shift towards the products, and ΔG will decrease.
4. Step 4: Analyze reaction (b) 2 HBr(g) ⇌ H₂(g) + Br₂(g). Increasing the partial pressure of H₂ will increase the numerator of Q, thus increasing Q. Since Q > K, the reaction will shift towards the reactants, and ΔG will increase.
5. Step 5: Analyze reaction (c) 2 H₂(g) + C₂H₂(g) ⇌ C₂H₆(g). Increasing the partial pressure of H₂ will increase the denominator of Q, thus decreasing Q. Since Q < K, the reaction will shift towards the products, and ΔG will decrease.