Question

Which of the following correctly describes the equilibrium constant for the gas-phase reaction between H₂ and O₂ to form gaseous H₂O

a.) Kc = [H₂O]/[H₂][O₂]
b.)Kc = [H₂O]₂/[H₂][O₂]
c.) Kc = [H₂O]₂/[H₂]₂[O₂]
d.) Kc = [H₂][O₂]/[H₂O]
e.) Kc = [H₂O]

Answer 1

The equilibrium constant (Kc) for the gas-phase reaction of H₂ with O₂ to form H₂O is correctly expressed as [H₂O]² / ([H₂]²[O₂]), which matches with the chemical equation 2H₂(g) + O₂(g) → 2H₂O(g) following the law of mass action.

Step-by-step explanation:

The correct formula for the equilibrium constant (Kc) for the reaction between hydrogen gas (H₂) and oxygen gas (O₂) to form gaseous water (H₂O) is as follows:

Kc = [H₂O]² / ([H₂]²[O₂])

This expression is derived from the balanced chemical equation for the formation of water from hydrogen and oxygen gases, which is 2H₂(g) + O₂(g) → 2H₂O(g). According to the law of mass action, the equilibrium constant expression for a reaction is the product of the concentrations of the products raised to the power of their respective coefficients, divided by the product of the concentrations of the reactants also raised to the power of their respective coefficients. Since the coefficients for H₂ and H₂O in the balanced equation are 2, and O₂ is 1, their powers in the equilibrium expression are squared for H₂ and H₂O, and to the first power for O₂. Therefore, option c is the correct description of Kc for this reaction.