Entropy / electrode potentials

What happens if a system becomes more random?

Energy is spread out more, the entropy change will be positive

What happens if a system becomes less random?

Energy becomes more concentrated and entropy change will be negative

What is the more negative system?

Greatest tendency to be oxidised and lose electrons, reacts from right to left (it is reversed)

What is the most positive system?

Greatest tendency to be reduced and gain electrons, reacts from left to right

What is a primary cell?

Non-rechargeable, only can be used once. Reactions cannot be reversed

What are secondary cells?

Rechargeable. Cell reaction that produces electrical energy can be reversed. So the chemicals can be regenerated

What are the oxidation and reduction reactions for alkali hydrogen fuel cells?

Oxidation: H2+2OH- = 2H2O + 2e-

Reduction: 1/2O2 + H2O + 2e- = 2OH-

Overall: H2+1/2O2 = H2O

What are the oxidation and reduction reactions for acid hydrogen fuel cells?

Oxidation: H2 = 2H+ + 2e-

Reduction: 1/2O2 + 2H+ + 2e- = H2O

Overall: H2 + 1/2O2 = H2O