The final composition of all the gases in the mixture has been [tex]\rm 80\;cm^3[/tex] Nitrogen, [tex]\rm 10\;cm^3[/tex] oxygen, [tex]\rm 5\;cm^3[/tex] carbon dioxide, and [tex]\rm 10\;cm^3[/tex] water (steam). Thus, the correct option is A.
The mixture of air has been composed of 20 % oxygen and 80 % nitrogen. The volume of air has been [tex]\rm 100\;cm^3[/tex]. Thus, the volume of oxygen and nitrogen in the air has been:
The volume of oxygen, [tex]V_O_2=20\;\rm cm^3[/tex]
The volume of nitrogen, [tex]V_N_2=80\;\rm cm^3[/tex]
Since the reaction, the nitrogen has been remained unused, thus the final composition of nitrogen has been [tex]\rm 80 \;cm^3[/tex].
The balanced equation for the reaction of methane with oxygen has been:
[tex]\rm CH_4\;+\;2\;O_2\;\rightarrow\;CO_2\;+\;2\;H_2O[/tex]
According to Avogadro's law, the presence of gases at the same temperature has volume proportional to the moles of the gases.
Thus, from the balanced chemical equation:
[tex]\rm 1\;cm^3\;CH_4=2\;cm^3\;O_2[/tex]
Thus,
[tex]\rm 5\;cm^3\;CH_4=10\;cm^3\;O_2[/tex]
Since the available oxygen has been [tex]\rm 20\;cm^3[/tex], the remaining oxygen after the reaction has been [tex]\rm 10\;cm^3[/tex].
Thus, the final composition of oxygen has been [tex]\rm 10\;cm^3[/tex].
Methane has been the limiting reactant. Thus, the concentration of carbon dioxide and water formed has been:
[tex]\rm 1\;cm^3\;CH_4=1\;cm^3\;CO_2\\5\;cm^3\;CH_4=5\;cm^3\;CO_2[/tex]
The final composition of carbon dioxide has been [tex]\rm 5\;cm^3[/tex].
[tex]\rm 1\;cm^3\;CH_4=2\;cm^3\;H_2O\\5\;cm^3\;CH_4=10\;cm^3\;H_2O[/tex]
The final composition of water (steam) has been [tex]\rm 10\;cm^3[/tex].
The final composition of all the gases in the mixture has been [tex]\rm 80\;cm^3[/tex] Nitrogen, [tex]\rm 10\;cm^3[/tex] oxygen, [tex]\rm 5\;cm^3[/tex] carbon dioxide, and [tex]\rm 10\;cm^3[/tex] water (steam). Thus, the correct option is A.
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