Oxidation, Reduction, Redox

Question 1

What are reducing agents?

Answer 1

Electron donor
substance that is oxidised, so loses electrons

Question 2

What are oxidising agents?

Answer 2

Electron acceptor
substance that is reduced, so gains electrons

Question 3

Oxidation numbers of the following:
Hydrogen
Chlorine
Oxygen
Ions

Answer 3

Hydrogen: always +1, except in hydrides (metal and hydrogen), where it is -1

Chlorine: always -1, but in compounds with F or O, it is +1

Oxygen: -2, except in peroxides it’s -1 and when F is present it’s +2, as F takes priority

Ions: same as charge on ion

Question 4

What has happened to the substance if there is an increase in oxidation number?

Answer 4

Oxidation (so it must be a reducing agent)

Question 5

What has happened to the substance if there is an decrease in oxidation number?

Answer 5

Reduction (so it must be an oxidising agent)

Question 6

Rules to balance half equations in redox

Answer 6

1. Write down species before and after reaction
2. Balance any atoms apart from hydrogen/oxygen
3. Balance any oxygens with H2O
4. Balance hydrogens with H+ ions
5. Balance charges with electrons