Which statement about the equilibrium constant is true? The value of Kc
A changes as reactant concentration changes.
B changes as temperature increases
C changes as product concentration charges.
D is inversely proportional to product concentrations
The correct answer and explanation is:
The correct answer is B: changes as temperature increases.
The equilibrium constant, KcK_c, is a value that represents the ratio of the concentration of products to reactants at equilibrium for a given chemical reaction. Its value is determined by the specific reaction and temperature.
Here’s an explanation of why B is correct:
- Effect of Temperature on KcK_c:
The value of the equilibrium constant is temperature-dependent. According to Le Chatelier’s principle, if the temperature of a system is changed, the system will shift to counteract that change, potentially altering the concentrations of reactants and products. For exothermic reactions (reactions that release heat), increasing temperature shifts the equilibrium to favor the reactants, leading to a decrease in KcK_c. In contrast, for endothermic reactions (reactions that absorb heat), increasing temperature shifts the equilibrium to favor the products, causing an increase in KcK_c. Thus, the equilibrium constant changes as temperature increases.
Now, let’s address the other choices:
- A: changes as reactant concentration changes.
This statement is incorrect because the equilibrium constant is independent of the concentrations of the reactants or products. The concentrations of reactants and products can change, but the value of KcK_c remains the same, assuming the temperature is constant. - C: changes as product concentration changes.
Similar to choice A, the concentration of products does not change the equilibrium constant. What changes is the position of the equilibrium—how much of the reactants and products are present—but the value of KcK_c itself is only affected by temperature. - D: is inversely proportional to product concentrations.
This is incorrect. The equilibrium constant is not inversely proportional to product concentrations. It reflects a ratio of products to reactants, and this ratio remains constant at a given temperature.
In summary, the equilibrium constant changes with temperature but not with changes in concentration.