CHEMICAL EQUATION | IONIC EQUETIONS

IONIC EQUATIONS

Ionic Equations

The Different Between Molecular Equations and Ionic Equations

Differentiate between molecular equations and ionic equations

Ionic equations are equations in which the reacting substances are represented in ionic forms after the elimination of spectator ions. In other words, ionic equations are those equations represented in such a way that spectator ions are not included in the final equation. Spectator ions refer to those ions, which do not change during the reaction i.e. they do not take part in a chemical reaction.

In order to be able to derive an ionic equation from a molecular equation, one must be acquainted with the solubility rules as outlined below:

•     All sodium, potassium and ammonium salts are soluble.
•     All nitrates, chlorates and acetates are soluble.
•     All binary compounds of the halogens (other than F) with metals are soluble, except those of silver, copper, lead and mercury (lead halides are soluble in hot water).
•     All sulphates are soluble except those of silver, lead, mercury (I), barium, strontium and calcium.
•     All carbonates, sulphites and phosphates are insoluble except those of ammonium and alkali metal (Group I) cations.
•     All hydroxides are insoluble except those of ammonium, barium and alkali metal (Group I) cations.
•     All sulphides are insoluble except those of ammonium, alkali metal (Group I) cations and alkali earth metal (Group II) cations.
•     All oxides are insoluble except those of calcium, barium and alkali metal (Group 1) cations; these soluble ones actually react with the water (hydrolyse) to form hydroxides.

Balanced Ionic Equations

Write balanced ionic equations

Steps for writing balanced ionic equations

1.     Write a balanced formula equation for the reaction.
2.     Split all soluble reactants and products into individual ions, clearly indicating their state symbols. Remember that substances that exists as molecules such as water, gasses and concentrated mineral acids, precipitates and neutral atoms do not consist of ions and hence do not ionize in water.
3.     Cancel out all the ions which appear on both sides of the equation (spectator ions). These are the ions which remain unchanged in the reaction.
4.     Re-write the remaining ions. This is the net ionic equation for that reaction.

Example 3

Consider the reaction for neutralization of hydrochloric acid with sodium hydroxide.

    Step 1: HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)

    Step 2:H+(aq)+Cl-(aq)+Na+(aq)+OH-(aq)→ Na+(aq)+Cl-(aq) + H2O(l)

    Step 3: :H+(aq)+Cl-(aq)+Na+(aq)+OH- (aq) → Na+(aq)+Cl-(aq) + H2O(l)

    Step 4: H+(aq)+ OH-(aq) → H2O(l)