The four basic types of reactions are:
1. Direct combination or Synthesis
This type of reaction involves two or more reactants uniting to form a single product. An example of this type is the reaction of nitrogen with hydrogen to form ammonia.g:
N₂ + 3H₂ → 2NH₃
2. Decomposition reaction
This is a reaction in which a single reactant is decomposed or broken down into two or more products.
CaCO₃ → CaO + CO₂
3. Single replacement reaction
This is also called single displacement. A single free element replaces or is substituted for one of the elements in a compound. The free element is more reactive than the one it replaces.
Zn + 2HCI → H₂ + ZnCl₂
4. Double replacement reaction
This is also known as double displacement. A double replacement (or double-displacement) reaction is a reaction in which the positive and negative ions of two ionic compounds exchange places to form two new compounds. Double replacement reactions can form precipitates, gases, or molecular compounds. An example is shown below.
AgNO₃ + NaCl → AgCl + NaNO₃
Description of how rate relationships and activation energy are important in chemical reactions.
Once reactants have absorbed enough heat energy from their surroundings to attain the transition state, the reaction will proceed. The activation energy of a particular reaction determines the rate at which it will proceed. Hence, the higher the activation energy, the slower the chemical reaction will be.