Unit 7: Topic 6 - Properties of the Equilibrium Constant Flashcards
Explain why K is inverted when a chemical reaction is reversed.
For the initial chemical reaction, K is a fraction where the numerator is related to the concentration of the products, and the denominator is related to that of the reactants. If the chemical reaction is reversed, the products and reactants flip so that the numerator should now consist of reactant concentrations, and the denominator should consist of product concentrations. This new K value is equivalent to the inverted K, or 1/K.
When a chemical reaction is stoichiometrically multiplied by a constant c, explain why K is raised to the power of c.
For a reaction zA + yB –> xC + wD, we have K = [D]^w[C]^x/[B]^y[A]^z if all substances are aqueous or gaseous and are excluded from this otherwise. If the chemical reaction is multiplied by a constant c, the exponents of all the concentrations are multiplied by c. Mathematically, the new K value is equivalent to K^c. If a reaction is flipped, this is equivalent to multiplying the coefficients by -1 (products become reactants and vice versa).
When reactions are added together, explain why the K for the resulting reaction is equal to the product of all the separate K’s of the original reactions.
K is directly proportional to the concentrations of the products and inversely proportional to the concentrations of the reactants. If we add together multiple reactions, we can group all the products and all the reactants. The new K value is directly proportional to ALL of these products and inversely proportional to ALL of the reactants. It must be equal to the product of the separate K’s from each initial reaction.
For example: A –> 2B
K1 = ([B]^2) / ([A]^1)
C + D –> E + 2F
K2 = ([E]^1[F]^2) / ([C]^1[D]^1)
A + C + D –> 2B + E + 2F
K3 = ([B]^2[E]^1[F]^2) / ([A]^1[C]^1[D]^1) = K1 * K2
Why do all of the properties of K apply to Q?
Q and K have almost the same form; K is equivalent to the ratios of the products and reactants at equilibrium, and Q is equal to this ratio under the initial conditions. Therefore, all properties of K listed above apply to Q.
