Energy & Redox

Question 1

How to write ionic equations

Answer 1

1. Write the chemical equation for this reaction, including state symbols.
2. Rewrite the equation with the ions in solution separate.
3. Rewrite the equation with the unchanged ions removed.

Question 2

Half equations

Answer 2

Add num of electrons to balance charge

Question 3

Oxidising agent

Answer 3

Electron acceptor

E.g. H2SO4, Al3+ & Cl2

Question 4

Reducing agent

Answer 4

Electron donor

E.g. Na, O2- & S2O32-

Question 5

Oxidation number

Answer 5

A measure of the number of electrons that an atom uses to bond with atoms of another element

Question 6

Oxidation

Answer 6

Lose of electrons/ an increase in oxidation number

Question 7

Reduction

Answer 7

Gain of electrons/ decrease in oxidation number

Question 8

Rules of oxidation number

Answer 8

1. Pure elements always have an oxidation number of 0
2. All group 1 atoms always adopt the +1 oxidation state in their compounds.
   b. All group 2 atoms always adopt the +2 oxidation state in their compounds.
   c. Aluminium always adopts the +3 oxidation state in its compounds.
3. Fluorine always adopts the -1 oxidation state in its compounds.
4. Hydrogen adopts the +1 oxidation state unless previous rules apply.
5. Oxygen adopts the -2 oxidation state unless previous rules apply.
6. The oxidation numbers of all other atoms in their compounds can vary.