Question

Hello, I was doing an experiemnt on thermodynamics of an electrochemical cell and I have a few questions afterwards. I noticed that when I put the Cu strip in the Cu(NO3)2 stock solution that the voltages changed when it was lowered or raised in the solution. I was wondering if you guys knew why that would happen? The cell I constructed was Pb/Pb^2+||Cu^2+/Cu

(Yes the Cu strip has already been in the solution)......when we had to get three voltage readings for a certain temperature the values vaired drastically depending on how far the strip was in the solution. (To get the different voltage readings the clamp had to be clipped and unclipped three times)

Answer 1

Definitely, it can be stated that the voltage response is dependent on how far the Cu strip is dipped in Cu(NO₃)₂ solution. As Cu strip plays the role of cathode here, reduction occurs and Cu ion is plated on the Cu strip by consuming electron. So, when Cu strip is dipped more, Cu2+ ions gets more surface area to be plated on Cu strip and more reduction of Cu2+ ion will occur, thereby producing change in voltage. By the movement of Cu strip more inside the solution, actually electrolyte solution gets access to more surface area of Cu strip which alters the voltage as active material on cathode increases by this process.