Answer – A coefficient is a number that precedes the formula of a reactant/product in a chemical equation. It indicates how many molecules of that compound must be present for the equation to be balanced.
Explanation:
While writing a chemical equation, it’s important to bear in mind that matter is neither created nor destroyed (law of conservation of mass). Thus, the number of atoms of each element on the reactants side is always equal to the number of atoms of each element on the products side. Only then is the equation considered balanced.
Coefficients are the numbers added in front of the formulas of reactants and products to balance the chemical equation. They indicate the number of atoms/molecules of each element that is a part of the reaction.
Unlike subscripts, coefficients may be changed while balancing an equation. They are also applied to each element making up a compound. A reactant/product without a number in front of it is always assumed to have a coefficient of 1.
Example:
In the above equation, H₂ has a coefficient of 2, O₂ has a coefficient of 1, and H₂O has a coefficient of 2.
