Final answer:
Unable to calculate the exact equilibrium concentration of Zn²+ without the equilibrium constant for the reaction of Zn(CN)₄²− in water, the expected concentration of Zn²+ at equilibrium is significantly lower than any of the provided options.
Step-by-step explanation:
The equilibrium concentration of Zn²+ in a 0.30-M solution of Zn(CN)₄²− can be determined by recognizing the complex ion equilibrium. The complex ion Zn(CN)₄²− dissociates in water to form Zn²+ and 4 CN− ions:
Zn(CN)₄²−(aq) ↔ Zn²+(aq) + 4CN−(aq)
However, since Zn(CN)₄²− is a strong complex, the backward reaction is favored and the concentration of Zn²+ at equilibrium is expected to be very low. In a typical complex ion equilibrium problem, one would use the equilibrium constant (K) specific to the reaction and set up an ICE table (Initial, Change, Equilibrium). However, without a given equilibrium constant for this specific equilibrium (which is not provided in the provided examples), we can't calculate the exact concentration. The concentration of Zn²+ is likely to fall within the order of magnitude of the given example where the concentration of Zn²+ in a similar situation led to a value of 5.7 × 10∗12 M. Thus, the equilibrium concentration of Zn²+ in this problem would be significantly lower than any of the choices given (0.30 M, 0.15 M, 0.10 M, or 0.05 M), and the question might be missing proper information or is otherwise flawed.