Chemical Reactions and Equations
In a chemical reaction, at least one of the following will occur:
Change in state
Change in colour
Evolution of a gas
Change in temperature
Formation of a precipitate
A chemical equation is the symbolic representation of a chemical reaction in the form of
chemical formulae, signs, symbols, and directions. In which the reactant entities are given
on the left-hand side and the product entities on the right-hand side.
Balanced chemical equation
Reactants → Products
LHS RHS
Total number of atoms on the LHS = Total number of atoms on the RHS
How to balance an equation
Write reactants and products
Balance the maximum number of a particular atom on both sides
Balance other atoms
A complete balanced equation should look like
CO g + 2H2 g →340 atm CH3OH l
Types of reactions
Combination reaction
o Two or more reactants combine to form one single product.
Examples: CaO s + H2O l → Ca(OH)2 aqCalcium oxide Water Calcium hydroxid
e (Quick lime) (Slaked lime) C s + O2 g → CO2 gCarbon Oxygen Ca
rbon dioxide 2H2 g + O2 g → 2H2O lHydrogen Oxygen Water
Exothermic reaction – Heat gets released in the reaction. Most combination reactions are
exothermic. For example,
In a chemical reaction, at least one of the following will occur:
Change in state
Change in colour
Evolution of a gas
Change in temperature
Formation of a precipitate
A chemical equation is the symbolic representation of a chemical reaction in the form of
chemical formulae, signs, symbols, and directions. In which the reactant entities are given
on the left-hand side and the product entities on the right-hand side.
Balanced chemical equation
Reactants → Products
LHS RHS
Total number of atoms on the LHS = Total number of atoms on the RHS
How to balance an equation
Write reactants and products
Balance the maximum number of a particular atom on both sides
Balance other atoms
A complete balanced equation should look like
CO g + 2H2 g →340 atm CH3OH l
Types of reactions
Combination reaction
o Two or more reactants combine to form one single product.
Examples: CaO s + H2O l → Ca(OH)2 aqCalcium oxide Water Calcium hydroxid
e (Quick lime) (Slaked lime) C s + O2 g → CO2 gCarbon Oxygen Ca
rbon dioxide 2H2 g + O2 g → 2H2O lHydrogen Oxygen Water
Exothermic reaction – Heat gets released in the reaction. Most combination reactions are
exothermic. For example,
