key term - Reaction quotient (Q)

Definition

The reaction quotient, Q, is a measure of the relative amounts of products and reactants present in a reaction mixture at any given point in time. It is calculated using the same expression as the equilibrium constant but with current concentrations or partial pressures.

5 Must Know Facts For Your Next Test

1. Q is calculated using the formula: $Q = \frac{[products]}{[reactants]}$, where concentrations are raised to the power of their coefficients in the balanced equation.
2. When Q < K (the equilibrium constant), the reaction proceeds in the forward direction to reach equilibrium.
3. When Q > K, the reaction proceeds in the reverse direction to reach equilibrium.
4. Q can be used to determine whether a system is at equilibrium, not yet reached it, or has surpassed it.
5. Unlike K, which is constant for a given reaction at a specific temperature, Q changes as concentrations or partial pressures change.

Review Questions

Related terms

Equilibrium Constant (K): A constant that expresses the ratio of concentrations of products to reactants at equilibrium for a given reaction.

Le Chatelier's Principle:

A principle stating that if a dynamic equilibrium is disturbed by changing conditions, the position of equilibrium moves to counteract the change.

Dynamic Equilibrium:

The state where the rate of the forward reaction equals the rate of the reverse reaction, resulting in no net change in concentration of reactants and products.