CHEMISTRY COMMUNITY

How do you know which side the platinum bar goes on in the cell diagram?

Its the side whose reaction does not already involve a solid metal and therefore platinum is added as an electrode to conduct the reaction.

You put it whenever the anode or cathode components are not solid. For example, if you have H+(aq)|H2(g), you will need to have Pt(s). This applies to when you have two aqueous solutions too. Another external electrode you can use is graphite: C(gr)

The side where there is no solid electrode has platinum.

Whichever side does not have an electrode uses platinum as its electrode