iGCSE Chemistry (0620) Core:11.2 Naming organic compounds: Exam Style Questions Paper 1- New Syllabus
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✅ Answer: (B) W and Z
▶️ Answer/Explanation
Detailed solution:
Natural gas is primarily composed of methane ($\text{CH}_4$), typically making up around 80-95% of its composition. The remaining percentage consists of smaller amounts of other hydrocarbons such as ethane, propane, and butane. Looking at the bar charts, option D shows methane as the largest component by far, taking up the majority of the bar, with only a small portion dedicated to other hydrocarbons. This accurately represents the composition of natural gas, where methane is the main constituent. The other options show different distributions that do not match the true composition of natural gas.
▶️ Answer/Explanation
Detailed solution:
Ethanol is an alcohol with the molecular formula $\mathrm{C_2H_5OH}$ or $\mathrm{CH_3CH_2OH}$. Its displayed formula shows two carbon atoms connected by a single covalent bond. The first carbon is bonded to three hydrogen atoms ($\mathrm{CH_3}$–), and the second carbon is bonded to two hydrogen atoms and an –OH (hydroxyl) group (–$\mathrm{CH_2OH}$). Looking at the four diagrams, the one with two carbons, five hydrogens, and one –OH group in this exact arrangement is ethanol. Methanol has only one carbon, methanoic acid and ethanoic acid contain a –COOH carboxyl group rather than the –OH alcohol group. The structure matching the $\mathrm{C_2H_5OH}$ formula is option D.