text: what is the half reaction for the substance undergoing reduction when using cuso4.5h2o , nacl , and h2o? my chem class did an experiment using a test tube with cuso4.5h2o layered with nacl then water. iron nails were placed in the water. cu+2 + 2e- ===> cu  reduction is the gain of electrons. copper cations gained electrons to be reduced to copper metal. oxidation is the loss of electrons. iron metal lost electrons to become ferrous chloride.  next time, have the teacher do the experiment with gelatin in a pie plate with na+cl- dissolved. add phenolphthalein to the gel for some reactions. add potassium ferrocyanide to the gel for others.