In a chemical equation, coefficients are the large whole numbers placed in front of chemical formulas to show how many molecules (or moles) of each substance take part in the reaction.
Key Points about Coefficients:
- Purpose
- They are used to balance chemical equations so that the number of atoms of each element is equal on both sides (Law of Conservation of Mass).
- What They Represent
- The relative number of molecules, formula units, or moles of each substance.
- Difference from Subscripts
- Coefficient: Number in front of a formula (applies to the whole molecule).
- Subscript: Small number within a chemical formula (applies only to the element it follows).
- Example: In H₂O, the “2” is a subscript (2 hydrogen atoms in one molecule of water).
If we write 3H₂O, the “3” is a coefficient (3 molecules of water, each containing 2 H and 1 O).
- Always in Whole Numbers
- Coefficients are written as the smallest whole numbers possible (fractions are simplified by multiplying the whole equation).