REDOX experiment INSPIRATIONS?

[Inspiration]

our choices are as follows:

 

combustions and fuel efficiency

prevention of metal corrosion

photographic process using silver (Ag) ions

voltage concentration of acid cells

voltag rate of H produced for electrolysis of salt solutions

determining the energy required to deposit 1kg of a USEFULL metal form its salt solution

best conditions for electroplting (voltage, concentration, plat surface)

determing the reactivity of certain metals ******

 

this experiment needs to be kept simple as we only have 1 70minute lesson to conduct it... any ideas, or leads to ideas for SIMPLE experiments in this fiels???? the asterisked points are experiments we have already conducted and are as such a last resort, any other help with the others would be much appreciated, but i have to keep it simple!!