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Stoichiometry is an important element of chemistry which deals with the relative quantities and products once tested for chemical reactions. In a balanced chemical reaction, the relations between quantities and products typically form a ratio of positive integers.In other words,stoichiometry is the balancing technique that balances mole number at both side in the equation, so the equilibrium is achieved in terms of atoms at both sides. It is used widely in testing of chemical reactions; and to manage balance reaction equation.

A balanced equation explain the stoichiometry of that reaction. It is being used in clinical analysis, agricultural researches, pharma, nutritional research and many more.

Let us try to understand the concept of Stoichiometry with a very basic example:

2H2 + O2 = 2H2O

In the above example of water molecule when 2 molecules of Hydrogen joint with 1 molecule of Oxygen then it produce 2 molecule of water.

Types of reactions in Stoichiometry:-


  •          Combination – to add 2 or more elements to form complex element
  •          Combustion – to form CO2 and H2O under reaction with O2
  •          Decomposition – to make reactants simpler
  •          Acid- Base – reaction that produce salt and water
  •          Single Displacement – to form two new elements by switching of single elements
  •          Double Displacement – to form two new elements by switching two elements.


[Propane (C3H8) burns in this reaction: C3H8 + 5O2 ----> 4H2O + 3CO2……….(Combustion Reaction)]

Question: If 200g of propane (C3H8) is burned, how many g of H2O will be produced?

Answer:  327.27 g H2O

Convert grams of C3H8 to moles of C3H8 then from mol of C3H8 to moles of H2O because we cannot calculate from gram value. Then convert from moles of H2O to grams of H2O.

Step 1: 200 g C3H8 = 4.54 mol C3H8.

Step 2:  As there is a ratio of 4:1 of H2O to C3H8 for every 4.54 mol C3H8 there are 18.18 mol H2O.

Step 3: Convert 18.18 mol H2O to g H2O. 18.18 mol H2O = 327.27 g H2O.

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