The displayed formula of ethanol is shown. Which of the following molecular formulae correctly represents ethanol?
Question 1 Report
The displayed formula of ethanol is shown. Which of the following molecular formulae correctly represents ethanol?
Answer Details
Count the atoms shown in the structure rather than recalling the formula.
Two carbon atoms are joined by a single bond. The left-hand carbon carries three hydrogens, one to its side and one above and below, and the right-hand carbon carries two hydrogens as well as a bond to the oxygen, which itself carries the last hydrogen. That gives \( \mathrm{CH_3CH_2OH} \), normally written \( \mathrm{C_2H_5OH} \). \( \mathrm{CH_3OH} \) is methanol and has only one carbon atom, so it cannot match a two-carbon chain. \( \mathrm{C_2H_6} \) is ethane and \( \mathrm{C_2H_4} \) is ethene; both ignore the oxygen drawn in the chain, and neither contains the \( \mathrm{-OH} \) group that makes a compound an alcohol.
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