WAEC Chemistry 2023 Paper

Concept:The correct option is found by checking each statement against the properties and formula of alkanes.Explanation:Alkanes have the general formula $\mathrm{C}_n\mathrm{H}_{2n+2}$.Alkanes react with chlorine by substitution, not by addition. Hence, option A is incorrect.Butane has a higher boiling point than propane because its molar mass is larger. Hence, option B is incorrect.Pentane has only three structural isomers: $n$-pentane, isopentane, and neopentane. Hence, option C is incorrect.For an alkane with $n = 49$ carbon atoms, the number of hydrogen atoms is:$H = 2n + 2 = 2(49) + 2 = 98 + 2 = 100$So, an alkane with 49 carbon atoms contains 100 hydrogen atoms.Answer:Option D is correct.