Chemical Equation Balancing

Overview

This lecture explains how to balance chemical equations using the algebraic (or algebraic method), illustrating each step with a worked example.

Chemical equations are balanced by ensuring atoms of each element are equal on both sides of the arrow.
The left side lists reactants, the right side lists products; the arrow acts as an equal sign.
The algebraic method assigns letters (A, B, C, etc.) as coefficients to each compound in the equation.

List all unique elements present in the equation, order does not matter.
Write an equation for each element, equating the total number of that atom on each side.
Each compound's coefficient becomes a variable (A, B, …), forming a system of linear equations.
Select the variable that appears most often and assign it a simple value (often 2 or another even number).
Substitute known values into other equations and solve for the remaining variables by algebraic manipulation.

Use substitution and elimination methods to solve for all variables.
If fractional coefficients occur, multiply all coefficients by the lowest common denominator to obtain whole numbers.
Assign the final coefficients to each compound in the original chemical equation.

Verify each element has the same total number of atoms on both sides by recounting all atoms using the final coefficients.
The equation is balanced if all atom counts match.

Chemical Equation — a symbolic representation of a chemical reaction.
Reactant — substance present before the reaction (left of arrow).
Product — substance formed by the reaction (right of arrow).
Coefficient — number indicating how many molecules of a compound are involved.
Algebraic Method — balancing approach using variables and systems of equations.