Can someone help me determine the masses of these elements?

Question

I have this one problem I do not get at all.

"A 0.1153 gram sample of a pure hydrocarbon was burned in a C-H combustion train to produce 0.3986 gram of CO2 and 0.0578 gram of H2O. Determine the masses of C and H in the sample and the percentages of these elements in the hydrocarbon."

Please also show workings so I understand it! Thanks. Best answer will be chosen ASAP.

Answer 1

First, write the equation :
CxHy + (x+1/4y) O2 ---> x CO2 + y/2 H2O
m CO2 = 0.386 gr ,then count the mass of C in CO2
m C = ((Ar C x n) / Mr CO2) x total mass of CO2
m C = (12 x 1)/44 x 0.3986
m C = 0.108709 gr

with the same formula count the mass of H in H2O
m H = 2/18 x 0.0578
m H = 0.006442gr

or total mass of hydrocarbon - mass of C will give the same result.

% C = mass of C / total mass x 100%
% C = 0.108709 / 0.1153 x100 % = 94. 2836 %
% H = 0.006422 / 0.1153 x 100% = 5.7164 %

Answer 2

We are interested in determining the numbers x and y in the formula CxHy of the original hydrocarbon. We have:
CxHy + zO2 -> a CO2 + b H2O. The corresponding masses:
(12x+y...32).........(44)........(18)... The specified quantities:
(0.1153)............(0.3986)....(0.0578)
Determine the number of moles by dividing each quantitiy by the corresponding molecular weight. Do this for the oxygen also; the quantity is the difference between the total quantity of products and the quantity of hydrocarbon.

With the number of moles now at hand, you can divide each of these by the smallest number present to get the relative number of moles. And that will let you figure out the coefficients of the reaction. (It sounds harder than it is.)

Answer 3

mass of C the molar mass of CO2 =44 on this 44 12 are of carbon, so in 0.3896 g of CO2 there is 0.3896*12/44=1.062g of carbon.
For H2O molar mass 18 , with 2g of Hydrogen so in 0.578g of water there is 0.0578*2/18=0.0064g of Hydrogen
Cn Hm ---> n CO2 +m/2 H2O
molar mass of CO2 =44 and of H2O=18
so the mass of CO2 produced is proportional to 44n and that of H2O to 18m/2=9m
you can write 0.3986/0.0578 =44n/9m =6.896
44n =6.896*9m=62.07m
and n/m=1.41