Galvanic Corrosion in a galvanic cell

Question

I am doing an individual practical at school, which requires us to investigate the reactivity of metals, using galvanic cells. My initial proposal was to investigate the effectivity of different metal sacrificial anodes in preventing galvanic corrosion in a cell, where I set up a constant galvanic cell with Copper sulfate solution in one beaker and Zinc sulfate in the other, with electrodes of Copper and Zinc plates respectively. They would be linked with a salt bridge, and different sacrificial anodes would be placed in each of the electrodes overnight. Their mass and physical condition would be examined.

However, my chemistry teacher (who is not allowed to assist in our task) told me that this may be problematic, as placing a more reactive sacrificial anode in my electrodes would lead to a single displacement reaction (e.g. zinc plates in the CuSO4 solution would lead to ZnSO4 forming on the surface of the plates). I have not yet had the lesson time to carry out this experiment myself, but some friends who go to tutoring have told me that perhaps, my 0.05mol solution won't be concentrated enough for such a double displacement reaction to even occur.

Is this true, and if so, would there still be a way for me to carry out an experiment investigating the reactivity of metals? Thanks!

Answer 1

Look, Victor, you can't place your test metal "in" your anode. You may place it into your anodic solution *as* the anode *in place of* your copper anode (appropriately wired into a circuit!). Were it to act sacrificially, it would then dissolve, and zinc would plate out at the cathode (requires quite an electropositive element!). But, you don't want Cu(2+) next to it, since it will indeed locally react! use a non-reducible conducting cation there instead such as Na(+). If you were a potential cation (i.e. your test metal) would you want to be reducing an easy target like Cu(2+) or a difficult one like Zn(2+)?