[hartalinstalin69]

Chemicals used:CuSO4(aq), Al2(SO4)3, KNO3(salt bridge), copper and aluminium electrodes.

Hi, i recetly made an experiment based on electrical potencilas shown in link below, i was thinking that it at least seems to be better thant classic zinc-copper battery (potencial of 1.1V) becase it should have more voltage maybe (based on the potencilas it should had been aroud 2V) but in reality it is just around 0.5V.
Why is that???


2 e + Cu2+   ⇌   Cu(s)   0.337V
3 e + Al3+         ⇌       Al(s)        -1.662V
the link:https://en.wikipedia.org/wiki/Standard_electrode_potential_(data_page)

[Borek]

First thing to check: concentrations and potentials as calculated from the Nernst equation.

Then: Al is a poor choice in general. It gets quickly passivated with the oxide, so you don't have an Al/Al³⁺ system in your cell (ie. metallic Al is not able to directly oxidize to Al³⁺ and move into the solution). That means theoretical predictions based on the standard electrode potentials are useless.