CHAP 12 REDOX REACTIONS

Redox

Reduction + Oxidation (both happen together).

Oxidation

• gain of oxygen

• loss of hydrogen

• loss of electrons

e- in half equations are on rhs of equation

reduction

• loss of oxygen

• gain of hydrogen

• gain of electrons

e- in half equations are of LHS of equation

OIL RIG

Oxidation Is Loss, Reduction Is Gain.

Reducing agent

• donates/loses electrons, causes another to be reduced (gain e-) , itself oxidised, loses e-

Oxidising agent

accepts electrons, causes another to be oxidised (lose e-) , itself reduced (gains e-)

Agents and their products form…

conjugate redox pairs (e.g. Zn/Zn²⁺, Cu²⁺/Cu).

half equations

• show one side of the redox (either oxidation or reduction)

• combine half equations, electrons cancel

• balance everyt except O and H

• balance O by adding H2O

• balance H by adding H+ (protons)

• balance the atoms/charges

reactivity series : Metals lower in the series =

more reactive (stronger reducing agents).

reactivity series : ions higher in the series =

• stronger oxidising agents.

in the reactivity series, the more reactive metal displaces..

the less reactive metal from solution.

galvanic cells (AN OIL RIG CAT)

• Convert chemical → electrical energy.

• Two half-cells connected by a salt bridge and external circuit.

• Oxidation at anode (negative electrode).

• Reduction at cathode (positive electrode).

• Electrons flow from anode → cathode.

• Salt bridge allows ion movement to balance charge.

cells in society

primary and secondary

primary cells

non-rechargeable, discarded after use.

Secondary cells

rechargeable, used in modern batteries.