I've construct a galvanic cell with the Al strip putting in the Aluminum nitrate solution and Cu strip putting in the CuSO4 solution. KNO3 is used as the salt bridge in this experiment. The question is about how does changing the concentration of the copper sulfate solution affect the electrode potential in this galvanic cell. I use 5 different variables of the concentration of the copper sulfate, which are 1.5M, 1M, 0.5M 0.25M, and 0M which is distilled water.
I choose using 1M of concentration of CuSO4 as the example to calculate the theoretical value of the electrode potential by using Nernst equation. The following picture is my working process and my data table. I'm just wondering about do I do something wrong in my work. If I didn't make mistakes in my working process, why is the experimental value so differ from the theoretical value? When the copper sulfate is being replaced by water, why does it still have a voltage? When I replaced both copper sulfate and aluminium nitrate to water, why does it have a voltage?