How is Q different from K
K is always less than Q
Kis calculated only at equilibrium, Q is calculated at any point during the reaction
Kis always greater than Q
K is used for concentrations. Q is used for partial pressures
Kis for the forward reaction, Q is for the mverse reaction
The correct answer and explanation is :
The correct answer is:
Q is calculated at any point during the reaction, whereas K is calculated only at equilibrium.
Explanation:
Q (Reaction Quotient) and K (Equilibrium Constant) are both expressions that relate the concentrations or partial pressures of reactants and products in a chemical reaction. However, they differ significantly in their meanings and applications.
- K (Equilibrium Constant) is defined for a reaction when it has reached equilibrium. It represents the ratio of the concentration or partial pressures of products to reactants at equilibrium. The expression for K remains constant at a given temperature, regardless of how far the reaction has proceeded toward equilibrium.
- K is constant at equilibrium: This means that when the reaction reaches a state where the rates of the forward and reverse reactions are equal, the ratio of products to reactants stays constant at a particular temperature.
- Q (Reaction Quotient), on the other hand, is similar to K but it can be calculated at any point during the reaction, not just at equilibrium. Q is the ratio of the concentrations (or partial pressures) of products and reactants at any moment in time during the reaction. It is used to compare the current state of the reaction with the equilibrium state.
- Q can vary during the reaction: If Q is greater than K, the reaction will shift towards the reactants to reach equilibrium. If Q is less than K, the reaction will shift towards the products.
Key Differences:
- K is for equilibrium, Q is for non-equilibrium conditions.
- K remains constant at a given temperature and reflects the ratio at equilibrium.
- Q can change as the reaction progresses toward equilibrium.
Conclusion:
In summary, K is only relevant when the reaction is at equilibrium, and its value is fixed for a given temperature. In contrast, Q is applicable at any point during the reaction and is used to assess the direction in which the reaction will proceed to achieve equilibrium.
Here is a visual diagram highlighting the differences between the reaction quotient (Q) and the equilibrium constant (K). It shows that:
- K is only relevant at equilibrium and remains constant at a given temperature.
- Q can be calculated at any point during the reaction and varies as the reaction progresses.
The diagram also illustrates how the reaction shifts depending on whether Q is greater than or less than K.