A stoichiometric coefficient is the number placed in front of a chemical formula in a balanced chemical equation.
It shows how many units (moles, molecules, or atoms) of a substance take part in the reaction.
Key points about stoichiometric coefficients:
- They ensure the law of conservation of mass is followed (same number of each atom on both sides).
- They tell us the proportion in which reactants combine and products form.
- They apply to moles as well as individual particles. For example, if the coefficient is 2, it means 2 molecules or 2 moles of that substance.
- They are the numbers used in stoichiometric calculations to relate reactants to products.
Example (in words, not symbols):
If hydrogen reacts with oxygen to form water, the balanced equation says 2 molecules of hydrogen react with 1 molecule of oxygen to produce 2 molecules of water. Here, the coefficients 2, 1, and 2 show the ratio of hydrogen, oxygen, and water.
In short, a stoichiometric coefficient is the “multiplier” in a chemical equation that shows how much of each substance is involved in the reaction.