Chapter 1 · Chemistry
Chemical Reactions and Equations
A chemical reaction rearranges atoms — it never creates or destroys them. This chapter turns every skeletal equation into a balanced, classified, mass-checked statement of what actually happened in the beaker.
Equation Balancer
Set the coefficients so atoms on both sides match. The reaction only 'runs' when the equation is balanced.
Not balanced yet — count each element on the left and the right and adjust the coefficients (never the subscripts).
Reaction type
Displacement (redox)
Iron displaces hydrogen from steam to give iron(II,III) oxide.
Formula sheet
Law of conservation of mass
Σ mass(reactants) = Σ mass(products)
Total mass before a reaction equals total mass after it. This is why equations must be balanced.
Combination
A + B → AB
Two or more substances combine into a single product.
CaO + H₂O → Ca(OH)₂ (exothermic)
Decomposition
AB → A + B
One compound splits into two or more products using heat, light or electricity.
2FeSO₄ →(Δ) Fe₂O₃ + SO₂ + SO₃
Displacement
A + BC → AC + B
A more reactive element pushes out a less reactive one.
Fe + CuSO₄ → FeSO₄ + Cu
Double displacement
AB + CD → AD + CB
Ions are exchanged between two compounds; often a precipitate forms.
Na₂SO₄ + BaCl₂ → BaSO₄↓ + 2NaCl
Redox
Oxidation = gain of O / loss of H or e⁻
Reduction is the opposite. Both always happen together in the same reaction.