Petroleum fractions are made up of hydrocarbons. Which statement correctly describes what a hydrocarbon is?
Question 1 Report
Petroleum fractions are made up of hydrocarbons. Which statement correctly describes what a hydrocarbon is?
Answer Details
The name says it: a hydrocarbon is a compound containing only hydrogen and carbon, with no other element present. Methane \(\text{CH}_4\), octane \(\text{C}_8\text{H}_{18}\) and the alkanes generally, formula \(\text{C}_n\text{H}_{2n+2}\), are all hydrocarbons, and crude oil is a mixture of thousands of them.
Something made only of carbon atoms is an element such as graphite or diamond, not a compound and not a hydrocarbon. Adding oxygen to carbon and hydrogen makes a different family altogether, for example ethanol \(\text{C}_2\text{H}_5\text{OH}\), which is a compound of three elements and therefore not a hydrocarbon. A mixture of water and carbon is not a compound at all, since its components are not chemically joined.
The word "only" is what earns the mark; do not omit it.
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