chemistry and enthalpy question?

Question

A 10.0-g sample of a mixture of CH4 and C2H4 reacts with oxygen at 25.0oC and 1.00 atm to produce CO2(g) and H2O(l). If the reaction produces 544 kJ of heat, what is the mass percentage of CH4 in the mixture?

No, actually I am trying to see someone's thought process in answering this question because everytime I have solved it I have gotten the wrong answer- i'm not sure where I go wrong. I set up the problem this way: delta H1 CH4 +2O2=>CO2 +2H2O = -890.2kJ
delta H2 C2H4 +3O2=>2CO2+2H2O = -1411.1
CH4= x moles C2H4 = y moles
544= -890.2x+-1411.1y
10=16x+28.1y
so i tried to solve for x but it never worked for both equations i know the %mass of CH4 is x16/10 so where am I going wrong...I keep getting around .36 for y which cant be right

Answer 1

CH4 +2O2=>CO2 +2H2O = -890.2kJ
delta H2 C2H4 +3O2=>2CO2+2H2O = -1411.1

12g(CH4) yields 890.2 kJ,
28g(C2H4) yields 1411.1 kJ,
(CH4) yields 890.2 kJ/12 g = 74.183 kJ/g
(C2H4) yields 1411.1 kJ/ 28 g = 50.396 kJ/g
let
x = mass of CH4
y = mass of C2H4
x + y = 10
74.183x + 50.396y = 544
50.396x + 50.396y = 503.96
28.787x = 40.036
x = 1.39 g
(100%)*(x/10) = 13.9%

Answer 2

do you have indiviual enthalpies of combustion for ch4 and c2h4 given?Then x+16 +y*28=10
then use hesss law
and get another eq and solve
IM me for detailed discussion.
I think this should work

Answer 3

Do you have a specific question at all? Or are you just posting the questions verbatim in hopes that someone will do your homework for you? I'm not willing to do that, but if you do have a specific question then I might try to help.