Balancing Chemical Equations

Balancing Chemical
Equations

Law of Conservation of Mass

• In a chemical reaction, matter is not created or destroyed.

• Total mass of the reactants = total mass of the products.

Why do we need to balance?

• Balancing equations makes sure our written equation matches what really happens in nature.

• A chemical equation shows what happens in a reaction, but if it’s not balanced, it’s not accurate.

• Every atom that goes into a reaction has to come out somewhere - we can’t just “lose” or “create” atoms.

• It also helps us to calculate the amounts of reactants/products, size of the reaction, and whether energy is released or absorbed.

• Count the number of each type of atom on both sides.

• Only add coefficients (big numbers in front).

• Never change subscripts (the small numbers).

• Balance one element at a time.

• Balance oxygen and hydrogen last.

• Re-check all atoms at the end.

Rules of Balancing

Equation: H₂ + O₂ → H₂O

• Step 1: Count atoms

  • Left: H = 2, O = 2

  • Right: H = 2, O = 1

• Step 2: Balance oxygen → 2H₂ + O₂ → 2H₂O

• Step 3: Check again

  • Left: H = 4, O = 2

• Right: H = 4, O = 2
  ✅ Balanced!

Na + Cl₂ → NaCl

Let's do one together!

Na + Cl₂ → NaCl

Let's do one together!

​Step 1: Count atoms

Step 2: Balance chlorine

Step 3: Check

Na + Cl₂ → NaCl

Let's do one together!

2Na + Cl₂ → 2NaCl

Time to Practise