2.5    Stoichiometry and Equations

Stoichiometry

• Stoichiometry is the proportion of things either reacting or combining
• In compounds, it refers to the ratio in which the atoms are combined For example, water, H2O has a stoichiometry of 2 hydrogen to 1 oxygen.
• It also refers to the reacting proportions in a chemical For example:

2H2 + O2 → 2H2O

The stoichiometry shows that 2 moles of hydrogen react with 1 mole of oxygen to form 2 moles of water.

Ionic equations

• Steps to construct net ionic equations:
  1. Write the balanced molecular equation
  2. Write the complete ionic equation by splitting it into ions(if possible).
  3. Cancel out the spectator (Spectator ions are ions that present in the mixture but do not participate in the reaction.)
  4. Write down the ‘leftovers’, that is the net ionic equation