Qc is defined as which of the following?

Qc is defined as which of the following?

• A. The total concentration of all species
• B. The sum of products' concentrations
• C. The sum of reactants' concentrations
• D. The reaction quotient expressed using products and reactants concentrations

Answer: (D)

Qc measures the current state of a reaction by comparing how much product is present to how much reactant is present, using their concentrations. For a typical reaction aA + bB ⇌ cC + dD, Qc is defined as ([C]^c [D]^d)/([A]^a [B]^b). This uses the instantaneous concentrations of the species, not the total or sum of all species. It’s the reaction quotient expressed with product and reactant concentrations, and it becomes equal to the equilibrium constant Kc when the system is at equilibrium. If Qc differs from Kc, it indicates the direction in which the reaction must move to reach equilibrium.

Qc measures the current state of a reaction by comparing how much product is present to how much reactant is present, using their concentrations. For a typical reaction aA + bB ⇌ cC + dD, Qc is defined as ([C]^c [D]^d)/([A]^a [B]^b). This uses the instantaneous concentrations of the species, not the total or sum of all species. It’s the reaction quotient expressed with product and reactant concentrations, and it becomes equal to the equilibrium constant Kc when the system is at equilibrium. If Qc differs from Kc, it indicates the direction in which the reaction must move to reach equilibrium.