28 . 0 L of CO _ 2 is produced on complete combustion of 16 . 8L...

Complete combustion of ethene and methane mixture produces carbon dioxide.
Let, Volume of ${C}_{2}{H}_{4}$ is $x$ litre

${C}_{2}{H}_{4} + 3{O}_{2} \to 2{CO}_{2} + 2{H}_{2}O$

Initial volume of carbon dioxide 0
Final volume of carbon dioxide $2x$

${CH}_{4} + 2{O}_{2} \to {CO}_{2} + 2{H}_{2}O$

Initial volume of carbon dioxide is 0

Final volume of carbon dioxide is $( 16 . 8 - x )$

Total volume of ${CO}_{2} = 2x + 16 . 8 - x$

$⇒ 28 = 16 . 8 + x$

$x = 11 . 2L$

${n}_{{CH}_{4}} = \dfrac{PV}{RT} = \dfrac{1 \times 5 . 6}{0 . 082 \times 298} = 0 . 229mole$

${n}_{{C}_{2}{H}_{4}} = \dfrac{11 . 2}{0 . 082 \times 298} = 0 . 458mole$

$∴$ Heat evolved using standard enthalpy of combustion $= 0 . 229 \times 900 + 0 . 458 \times 1400$

$= 206 . 1 + 641 . 2$

$= 847 . 3kJ$