what can we say about the EA for an exothermic reaction?
a...must be <0
b...greater for reverse reaction
c...greater for forward reaction
d...can't say anything
To determine what can be said about the equilibrium constant (Kc) for an exothermic reaction, we need to understand the relationship between temperature and Kc.
For an exothermic reaction, the forward reaction releases heat, and the reactants have higher potential energy than the products. When temperature increases, the equilibrium position shifts in favor of the reactants. This is because the system tries to counteract the added heat by absorbing some of it, which is accomplished by favoring the endothermic forward reaction.
Based on this information, we can conclude that the equilibrium constant (Kc) for an exothermic reaction will be affected by the temperature change. To be more specific:
a) The magnitude of Kc for an exothermic reaction can be less than 1 or smaller than 0, depending on the stoichiometry of the balanced chemical equation. Therefore, the statement that Kc must be <0 is incorrect and cannot be generalized.
b) The equilibrium constant for the reverse reaction will be smaller than the equilibrium constant for the forward reaction due to the shift in equilibrium caused by increasing temperature. This means that the statement that the equilibrium constant is greater for the reverse reaction is incorrect.
c) However, it is known that for an exothermic reaction, an increase in temperature will favor the reverse reaction. Therefore, the equilibrium constant for the forward reaction will be greater when compared to the equilibrium constant for the reverse reaction. Therefore, the correct answer is c) The equilibrium constant (Kc) is greater for the forward reaction in an exothermic reaction.
d) We can definitely say something about the equilibrium constant for an exothermic reaction, so the statement that we can't say anything is incorrect.
In summary, for an exothermic reaction, the equilibrium constant (Kc) will be affected by temperature, and it will be greater for the forward reaction.