Answer
See answer below.
Work Step by Step
Number of moles of water:
$4.14\ g\div 18.015\ g/mol=0.23\ mol$,
$0.46\ mol\ H$
Number of moles of $CO_2$:
$8.80\ g\div 44.01\ g/mol=0.20\ mol$,
$0.20\ mol\ C$
Since both have 4 carbons, $0.05\ mol$
Number of hydrogens:
$x\times 8+(0.05-x)\times 10=0.46$
$x=0.02\ mol$ butene, $1.12\ g$
Mass fraction:
Butene: $1.12/2.86\times 100\%=39.2\%$
Butane: $100\%-39.2\%=60.8\%$
