Introduction to Balancing Chemical Equations

Summary

The video introduces chemical equation balancing as a way to ensure an equation shows the same number of each type of atom before and after a reaction. The instructor uses molecule diagrams and atom-counting charts to explain how coefficients change the number of molecules—and therefore the number of atoms—in an equation.

Key Concepts

• Reactants are the substances before the arrow; products are the substances after it.
• An equation is balanced when both sides of the arrow have the same number of each type of atom.
• An equation with unequal atom counts is unbalanced. Chemists generally need to balance equations before using them in calculations.
• A coefficient is a number placed in front of a chemical formula. It indicates how many molecules of that substance are present and multiplies the count of every atom in the formula.
• A subscript is the small number within a formula. It indicates how many atoms of an element are in a molecule and must not be changed when balancing. Changing a subscript changes the substance itself—for example, changing H₂O to H₂O₂ changes water into hydrogen peroxide.

Balancing Method

1. Write the chemical formulas for the reactants and products.
2. Count each type of atom on both sides of the arrow, using a diagram or chart.
3. Identify any imbalances by finding elements with different atom counts on each side.
4. Add or adjust a coefficient in front of a compound to change its molecule and atom counts.
5. Recount all atoms, since changing one coefficient can affect more than one element.
6. Repeat until each element has matching counts on both sides.
7. Keep all subscripts unchanged; make adjustments only with coefficients.

Examples

• Hydrogen and chlorine: The initial equation, H₂ + Cl₂ → HCl, is unbalanced. Placing a 2 before HCl gives H₂ + Cl₂ → 2HCl, with two hydrogen atoms and two chlorine atoms on each side.
• Hydrogen and oxygen: The equation balances as 2H₂ + O₂ → 2H₂O. The instructor first adjusts the water coefficient to balance oxygen, then adjusts the hydrogen gas coefficient to balance hydrogen.
• Nitrogen and hydrogen: A chart helps track atom counts as coefficients are adjusted. The instructor balances nitrogen first, then uses the resulting hydrogen count to determine the coefficient for hydrogen.

The video closes by recommending repeated practice to build skill with balancing equations.

Speaker

• Tyler DeWitt — instructor and narrator