Question

Iso-octane reacts with oxygen:
A) Endothermically
B) Exothermically
C) Only some activation energy is required
D) Doesn’t react

Answer 1

Hint: The answer here is dependent on the fact that isooctane is the compound which is widely used in gasoline and thus the reaction with oxygen releases energy. Thus, the answer lies in this fact.

Complete step by step answer:
We have come across the organic chemistry concepts that deal with the chapters based on the processes of purification of compounds and also several concepts of hydrocarbons.
We shall now see the base of these concepts which will lead us to the required answer.
- Iso-octane that is 2,2,4 – trimethylpentane is an organic compound which has the chemical formula ${{C}_{8}}{{H}_{18}}$ is one of the isomers of octane.
- Iso – octane is an important component in the gasoline which is used in very large proportions for the increase of knock resistance of the fuel.
- Iso-octane is produced on a massive scale in the petroleum industry by the process of alkylation of isobutene with isobutene.
- Iso-octane is flammable and hence has to be managed carefully.
- This iso-octane reacts with oxygen to give carbon dioxide and water and thus this reaction is combustion reaction and thus are exothermic in nature that is they give off heat to the surroundings.
Thus, the reaction taking place is given below,
\[2{{C}_{8}}{{H}_{18}}(l)+5{{O}_{2}}(g)\to 16C{{O}_{2}}(g)+18{{H}_{2}}O(g)\]
Thus, the reaction of iso-octane with oxygen is exothermic in nature.

Therefore, the correct answer is option B) Exothermically.

Note: Almost always, the combustion reactions are exothermic in nature. The organic molecules when undergoes the combustion reaction, the products formed are carbon dioxide and water and also heat.