Count the Atoms
How many oxygen atoms are in 4NO₂
8 oxygen atoms
H₂ + O₂ → H₂O
2H₂ + O₂ → 2H₂O
CH₄ + O₂ → CO₂ + H₂O
CH₄ + 2O₂ → CO₂ + 2H₂O
NaOH + HCl → NaCl + H₂O
Already balanced
Substances at the start of a reaction.
Reactants
How many total atoms are in 3CaCO₃
15 total atoms
N₂ + H₂ → NH₃
N₂ + 3H₂ → 2NH₃
Fe₂O₃ + H₂ → Fe + H₂O
Fe₂O₃ + 3H₂ → 2Fe + 3H₂O
BaCl₂ + Na₂SO₄ → BaSO₄ + NaCl
BaCl₂ + Na₂SO₄ → BaSO₄ + 2NaCl
Substances formed in a reaction.
Products
How many hydrogen atoms are in 2NH₄NO₃
8 hydrogen atoms
Fe + O₂ → Fe₂O₃
4Fe + 3O₂ → 2Fe₂O₃
C₂H₆ + O₂ → CO₂ + H₂O
2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O
Ca(OH)₂ + HCl → CaCl₂ + H₂O
Ca(OH)₂ + 2HCl → CaCl₂ + 2H₂O
A number placed in front of a chemical formula.
Coefficient
How many oxygen atoms are in 3Al₂(SO₄)₃?
36 oxygen atoms
Mg + HCl → MgCl₂ + H₂
Mg + 2HCl → MgCl₂ + H₂
FeS₂ + O₂ → Fe₂O₃ + SO₂
4FeS₂ + 11O₂ → 2Fe₂O₃ + 8SO₂
Na₂CO₃ + HCl → NaCl + H₂O + CO
Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂
A small number in a chemical formula that shows number of atoms.
Subscript
How many total atoms are in 2Fe₂(SO₄)₃?
34 total atoms
Al + O₂ → Al₂O₃
4Al + 3O₂ → 2Al₂O₃
C₄H₁₀ + O₂ → CO₂ + H₂O
2C₄H₁₀ + 13O₂ → 8CO₂ + 10H₂O
Al₂(SO₄)₃ + Ca(OH)₂ → Al(OH)₃ + CaSO₄
Al₂(SO₄)₃ + 3Ca(OH)₂ → 2Al(OH)₃ + 3CaSO₄
The rule stating matter cannot be created or destroyed.
Law of Conservation of Mass