1. The problem statement, all variables and given/known data What is the concentration of the unknown Cu2+ solution? The reaction is Zn(s) + Cu2+(aq) -> Zn2+(aq) + Cu(s). The concentration of Zn2+ is 0.05 M 2. Relevant equations 3. The attempt at a solution I'm coming up with about 2 different answers, and I'm not sure which is correct. Using a graph of (Emf vs log Cu2+) I obtained the line y = -1.0967 - 0.02x and I'm not sure how to figure out the unknown copper concentration. Method 1 (I'm leaning towards this method): -1.08 V is the voltage obtained from the unknown. -1.08 V = -1.0967 - 0.02x x = -.835 10^x = 10^-.835 [Cu2+] = .146 M Method 2: I'm assuming E0 is the y intercept and -0.0592/2logQ is the slope, not positive if that is correct. E = E0 - 0.0592/2logQ Q = [Zn2+]/[Cu+2] -1.08 = -1.0967 - 0.0592/2 log Q [Cu+2] = .183 M Which is the correct method to use for finding the copper concentration?