Identify the equation for which Keq = [Cu+]2[S2-].
A) CuS(s) ⇌ Cu2+(aq) + S2- (aq)
B) 1/2Cu2S(s) ⇌ Cu+(aq) + 1/2 S2- (aq)
C) Cu2S(s) ⇌ 2Cu+(aq) + S2- (aq)
D) Cu2S(s) ⇌ Cu+(aq) + 2 S2- (aq)
E) none of the answers
The "K" in Keq stands for "Constant". The "eq" means that the reaction is at equilibrium. Very roughly, Keq tells you the ratio of Products/Reactants for a given reaction at equilibrium.
The correct answer is D) Cu2S(s) ⇌ Cu+(aq) + 2 S2- (aq).
This is because the equation given, [Cu+]^2[S2-], represents the concentration of Cu+ ions squared times the concentration of S2- ions. In order for the equation to match this expression, it needs to have 1 Cu+ ion and 2 S2- ions. The only equation that meets this requirement is equation D.
To identify the equation for which Keq = [Cu+]2[S2-], we need to understand Keq and how it relates to the balanced chemical equation.
Keq is the equilibrium constant, which is a ratio of the concentrations (or partial pressures) of the products to the concentrations (or partial pressures) of the reactants, with each raised to the power of their respective stoichiometric coefficients.
In this case, we have Keq = [Cu+]2[S2-]. The equation will have the same species (Cu+ and S2-) on both sides of the reaction, and their stoichiometric coefficients raised to the appropriate powers (2 for Cu+ and 1 for S2-).
Let's analyze the options:
A) CuS(s) ⇌ Cu2+(aq) + S2-(aq)
The stoichiometric coefficient for Cu2+ is 1, not 2. Therefore, this is incorrect.
B) 1/2Cu2S(s) ⇌ Cu+(aq) + 1/2S2-(aq)
The stoichiometric coefficient for Cu+ is 1, not 2. Therefore, this is incorrect.
C) Cu2S(s) ⇌ 2Cu+(aq) + S2-(aq)
The stoichiometric coefficients of Cu+ and S2- match the given equation. Additionally, [Cu+]^2 and [S2-] are correctly represented in the Keq expression. Therefore, this is the correct answer.
D) Cu2S(s) ⇌ Cu+(aq) + 2S2-(aq)
The stoichiometric coefficient for S2- is 1, not 2. Therefore, this is incorrect.
E) None of the answers
As we have identified the equation that matches the given Keq expression, option C is correct. Therefore, E is not the answer.
Therefore, the correct equation is C) Cu2S(s) ⇌ 2Cu+(aq) + S2-(aq).