Types of Chemical Reactions
Chapter 2 | Section 2: Synthesis, Decomposition, Displacement & Double Decomposition
1. Direct Combination (Synthesis)
A reaction in which two or more substances (elements or compounds) combine to form a **single** new substance.
General Form: $A + B \rightarrow AB$
Example: $2Mg + O_2 \rightarrow 2MgO$ (Magnesium Oxide)
Example: $2Mg + O_2 \rightarrow 2MgO$ (Magnesium Oxide)
2. Decomposition Reaction
A reaction in which a single compound breaks down into two or more simpler substances. Usually requires energy in the form of heat, light, or electricity.
- Thermal Decomposition: $2KClO_3 \xrightarrow{\Delta} 2KCl + 3O_2 \uparrow$
- Electrolytic Decomposition: $2H_2O \xrightarrow{\text{elec.}} 2H_2 + O_2$
- Photochemical Decomposition: $2AgCl \xrightarrow{\text{light}} 2Ag + Cl_2$
3. Displacement Reaction
A reaction in which a more reactive element displaces a less reactive element from its compound.
General Form: $A + BC \rightarrow AC + B$
Example: $Fe + CuSO_4 \rightarrow FeSO_4 + Cu \downarrow$
Example: $Fe + CuSO_4 \rightarrow FeSO_4 + Cu \downarrow$
4. Double Decomposition
A reaction in which two compounds react by an exchange of radicals to form two new compounds.
- Precipitation: An insoluble solid (precipitate) is formed.
$AgNO_3 + NaCl \rightarrow AgCl \downarrow + NaNO_3$ - Neutralization: An acid reacts with a base to form salt and water.
$NaOH + HCl \rightarrow NaCl + H_2O$
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