30cm^3 of a mixture of methane and ethyne require 70cm^3 of oxygen for complete combustion. Calculate the composition of the mixture.
Let X = cc CH4
and Y = cc C2H2
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equation 1 is X + Y = 30 cc
Combustion equations.
CH4 + 2O2 ==> CO2 + 2H2O
2C2H2 + 5O2 ==> 4CO2 + 2H2O
equation 2 is made up of
[cc O2 needed to burn CH4 + cc O2 needed to burn C2H2 = 70] so equation 2 is
X(2mols O2/1 mol CH4) + Y(5 mols O2/2 mols C2H2) = 70
Solve equation 1 and equation 2 simultaneously for X and Y and that will give you the composition. Post your work if you get stuck.