Stoichiometry

The branch of chemistry which deals with quantitative relationships between reactants and products in a balanced chemical equation is called stoichiometry.

Stoichiometry of reaction

The mole ratio in which the reactants combine together with the mole ratio in which products are formed is called stoichiometry of reaction.

Stoichiometric amounts

In a balanced chemical equation, the amounts of reactants and products are called stoichiometric amounts.

Stoichiometric calculations

The calculations based on stoichiometry are called stoichiometric calculations.

Assumptions for stoichiometric calculations

• All the reactants are completely converted into products.
• No side reaction is taking place.
• Law of conservation of mass and law of definite proportions are obeyed.

Laws employed in stoichiometry

• Law of conservation of mass.
• Law of definite proportions.

Relationships in stoichiometric calculations

There are several common relationship-types you will use:

1. Mass–mass relationship
   Mass of one substance is given and mass of another substance is to be calculated.
2. Mass–mole or mole–mass relationship
   Mass of one substance is given and moles of another substance are to be calculated (and vice versa).
3. Mole–mole relationship
   Moles of one substance are calculated from the moles of another.
4. Mass–volume or volume–mass relationship
   Mass of one substance is given and volume of another substance is to be calculated (or vice versa).

Tip: For practical stoichiometric problems always start by writing the balanced chemical equation, convert given masses to moles (using molar mass), use mole ratios from the balanced equation, then convert to required units.