1.3: Write balanced full and ionic equations, including state symbols, for chemical reactions

Definitions:

• Ionic Equation: An equation that shows the ions involved in the reaction as well as other non-ionic elements/compounds.
• Ion: An ion is formed when an atom gains or loses one or more electrons. Ions are charged particles. Ionic compounds are formed from ions.

You will be expected to know some ions off by heart, below is a list of the most common ones:

Ion	Symbol
Ammonium	NH₄⁺
Carbonate	CO₃²⁻
Hydrogen-carbonate	HCO₃⁻
Hydroxide	OH⁻
Nitrate	NO₃⁻
Phosphate	PO₄³⁻
Sulphate	SO₄²⁻

Examples:

1. Iron metal reacts with copper(ii)sulphate solution, the products are copper and iron(ii)sulpahte. Find the ionic equation for this reaction.

• Although not necessary I would recommend you to write down the symbol/stoichiometric equation, as it will help you visualise and balance the equation.
• In this case: 
• Fe(s) + CuSO₄(aq) → Cu(s) + FeSO₄(aq)
• As we can see this equation is already balanced.
• Next, you have to separate it into its ions (You may skip this step if you are able to identify spectator ions easily.):
• Fe(s) + Cu²⁺(aq) + SO₄²⁻(aq) → Cu(s) + Fe²⁺(aq) + SO₄²⁻(aq)
• Now you have to compare both sides of the equation and look for spectator ions, ions that do not change during the reaction. Which are: SO₄²⁻(aq)
• Finally re-write the ionic equation without the spectator ions.
• Fe(s) + Cu²⁺(aq)  → Cu(s) + Fe²⁺(aq) 

2. Balance and write the ionic equation of the following reaction: NaOH(aq)⠀+⠀Fe(NO₃)₂(aq)⠀→⠀NaNO₃(aq)⠀+⠀Fe(OH)₂(aq)

• First balance the equation:
• 2NaOH(aq)⠀+⠀Fe(NO₃)₂(aq)⠀→⠀2NaNO₃(aq)⠀+⠀Fe(OH)₂(s)
• Then separate into ions:
• 2Na⁺(aq) + 2OH⁻(aq) + Fe²⁺(aq) + 2NO³⁻(aq) → 2Na⁺(aq) + 2NO³⁻(aq) + Fe(OH)₂(s)
• Remove spectator ions:
• 2OH⁻(aq)  + Fe²⁺(aq) →  Fe(OH)₂(s)

Practice Question:

Question: Balance and write the ionic equation of the following reaction:

FeSO₄(aq) + H₂O₂(l) + H₂SO₄(aq) → Fe₂(SO₄)₃(aq) + H₂O(l)

Answer:

First, balance the equation: 2FeSO₄(aq) + H₂O₂(l) + H₂SO₄(aq) → Fe₂(SO₄)₃(aq) + 2H₂O(l)
Write out ions: 2Fe²⁺(aq) + 2SO₄²⁻(aq) + H₂O₂(l) + 2H⁺(aq) + SO₄²⁻(aq) → 2Fe³⁺(aq) + 3SO₄²⁻(aq) + 2H₂O(l)
Remove spectator ions: 2Fe²⁺(aq) + H₂O₂(l) + 2H⁺(aq) → 2Fe³⁺(aq) + 2H₂O(l)
Notice that even though there is Fe on both sides they do not have the same charge, Fe²⁺(aq)  ≠ Fe³⁺(aq)