Revising Chemical reaction got a couple of different questions.
1. Describe what a decomposition reaction is and give an example
2. Describe what a combustion reaction is and give an example
3. Explain how a displacement reaction occurs.
4. Scientists have classified reactions into different types. Explain why this is useful.
5. Oxygen is written as O2 in chemical reactions rather than just O. Explain why this is the case.
1. A decomposition reaction is a type of chemical reaction in which a chemical compound breaks down into several smaller molecules under suitable conditions. One example is thermal decomposition of calcium carbonate:
2. A combustion reaction is one in which a compound (or element) burns in air to produce oxidative products along with some heat and may be light. An example of a combustion reaction is burning of fossil fuel:
CxHy + O2 --> CO2 + H2O
3. A displacement reaction is a type of reaction where part of one reactant is replaced by another reactant. Single displacement reactions are reactions where one reactant replaces part of the other. This occurs through exit of leaving group and entry of incoming group in a single concerted step or, in two separate steps. Example is: AB + C → AC + B
4. One of the uses of classification of reactions is that it helps one understand the type of reaction without having to go into the details. Under such a scheme, a vast number of reactions can be elegantly categorized and memorized easily.
5. Barring inert gases, all elementary gases are diatomic. This is a direct corollary of Avogadro’s hypothesis. That is the reason why molecular oxygen is written as O2, instead of O in chemical reactions.