WAEC Chemistry 2023 Objective — Question 9
Question 9 of 50 from the West African Examinations Council (WAEC) Chemistry 2023 Objective paper, with the correct answer and a full explanation.
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Which of the following statements is correct?
- A. An alkane with 49 carbon atoms contains 100 hydrogen atomsCorrect
- B. Addition reactions occur between alkanes and chlorine
- C. Butane has a lower boiling point than pentane
- D. Pentane has five isomers
Explanation
Since the general formula of alkanes is CnH2n+2, an alkane with 49 carbon atoms will contain (2×49)+2 = 100 hydrogen atoms. The reaction between alkanes and chlorine is a substitution reaction, not addition. Butane is heavier than propane so has a higher boiling point than propane (not relevant to this comparison — butane's boiling point is in fact higher than propane's, and lower than pentane's, so option C is false). Pentane has three isomers, not five.
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