Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.
Answer:
Decomposition reactions are those in which a compound breaks down to form two or more substances. These reactions require a source of energy to proceed. Thus, they are the exact opposite of combination reactions in which two or more substances combine to give a new substance with the release of energy.
Decomposition Reaction:
CaCO3 (calcium carbonate) → CaO (calcium oxide) + CO2 (carbon dioxide)
Substances Involved:
- Calcium carbonate (CaCO3)
- Calcium oxide (CaO)
- Carbon dioxide (CO2)
Combination Reaction:
2 H2 (hydrogen) + O2 (oxygen) → 2 H2O (water)
Substances Involved:
- Hydrogen (H2)
- Oxygen (O2)
- Water (H2O)