A student is electroplating an electrode using copper sulphate solution. Based on the current measure during the experiment, the electrodes should be coated with 12.2 grams of copper. However, the electrode is only coated with 10.4 grams of copper. What is the percentage yield for the electroplating process?
The percentage yield is equal to the actual yield, that is what you actually got by performing the experiment, divided by the theoretical yield, that is what you should have gotten given how you set the experiment up, times 100 percent.
In the process described in the problem, which is known as electroplating, we apply an electrical current so that copper from the copper sulphate solution will plate onto an electrode in the form of solid copper. The chemical equation that describes this process is Cu²⁺ aqueous plus two electrons forming Cu solid. Since electrical currents are related to the flow of electrons, and we know how many electrons it takes to form solid copper, we can calculate a theoretical yield for this process.
The problem tells us that the electrode should be coated with 12.2 grams of copper. So, this is our theoretical yield. But when the student performed the experiment, they only got 10.4 grams of copper. So, that’s our actual yield. If we perform that calculation, we get 85.2459 percent. The actual and theoretical yield were both given to three significant figures. So, our answer should be rounded to three significant figures as well. So, the percentage yield for this process was 85.2 percent.