Question

One mole of hydrocarbon X on combustion produces four moles of carbon dioxide and four moles of water.

1. Write the equation for the combustion reaction.
2. Draw the structure of X.

Answer 1

(a) Combustion reaction: On combustion, 1 mole of hydrocarbon X gives 4 moles of carbon dioxide and 4 moles of water. Therefore, X contains 4 carbon atoms and 8 hydrogen atoms. Hence, its molecular formula is C₄H₈.

\[\ce{C4H8 +6O2 -> 4CO2 + 4H2O}\]

(b) X is butene. Its structural formula may be written as but-1-ene:

\[\ce{CH2 = CH -CH2 - CH3}\]

Therefore, hydrocarbon X is butene.