Complete combustion of a sample of a hydrocarbon in the presence of excess oxygen produces equal molar quantities of carbon dioxide and water. Which of the following could be the molecular formula of the compound?
a. C4H4
b. C2H6
c. C6H6
d. C8H8
e. C8H16
I know the answer is C2H6, but I need it explained. Thank you!
I think you are are wrong
2C2H6+11O2>>>4CO2 +6H2O;
CO2, H2O: notice the ratio of C,H has to be 1:2
To determine the molecular formula of the compound, we need to examine the balanced chemical equation for the complete combustion of a hydrocarbon.
The general equation for the complete combustion of a hydrocarbon is:
CₓHᵧ + (x + y/4)O₂ -> xCO₂ + (y/2)H₂O
In this equation, the hydrocarbon CₓHᵧ reacts with (x + y/4) moles of oxygen gas (O₂). It produces x moles of carbon dioxide (CO₂) and y/2 moles of water (H₂O), assuming complete combustion.
Comparing the given options to the balanced equation, we find that:
a. C4H4: This hydrocarbon has insufficient carbons (4) to produce an equal amount of CO₂ and H₂O.
b. C2H6: This hydrocarbon contains 2 carbon atoms and 6 hydrogen atoms. When combusted, it will produce 2 moles of CO₂ and 3 moles of H₂O, which matches the equal molar quantities mentioned in the question.
c. C6H6: This hydrocarbon contains 6 carbon atoms, but it cannot produce an equal amount of CO₂ and H₂O.
d. C8H8: This hydrocarbon also contains 8 carbon atoms, but it cannot produce an equal amount of CO₂ and H₂O.
e. C8H16: This hydrocarbon contains 8 carbon atoms and 16 hydrogen atoms. When combusted, it will produce 8 moles of CO₂ and 8 moles of H₂O, not the equal molar quantities mentioned in the question.
Therefore, the only molecular formula that could produce equal molar quantities of CO₂ and H₂O is C2H6, option b.
To determine which molecular formula could be the compound based on the given information, we need to analyze the balanced chemical equation for the complete combustion of a hydrocarbon.
The general formula for the combustion of a hydrocarbon is:
Hydrocarbon + Oxygen → Carbon Dioxide + Water
From the information given, we know that the balanced chemical equation for the combustion of the hydrocarbon in question is:
CnHm + (n + m/4)O2 → nCO2 + m/2H2O
Given that equal molar quantities of carbon dioxide and water are produced, we must have an equal number of moles of carbon and hydrogen atoms on both sides of the equation.
For option a) C4H4:
- There are 4 carbon atoms and 4 hydrogen atoms.
- The balanced equation would be: C4H4 + 5O2 → 4CO2 + 2H2O
- However, the ratio of carbon to hydrogen atoms is not the same on both sides of the equation, so option a) is not possible.
For option c) C6H6:
- There are 6 carbon atoms and 6 hydrogen atoms.
- The balanced equation would be: C6H6 + 7O2 → 6CO2 + 3H2O
- Again, the ratio of carbon to hydrogen atoms is not the same on both sides of the equation, so option c) is not possible.
For option d) C8H8:
- There are 8 carbon atoms and 8 hydrogen atoms.
- The balanced equation would be: C8H8 + 9O2 → 8CO2 + 4H2O
- The ratio of carbon to hydrogen atoms is the same on both sides of the equation, so option d) is a possibility.
For option e) C8H16:
- There are 8 carbon atoms and 16 hydrogen atoms.
- The balanced equation would be: C8H16 + 12O2 → 8CO2 + 8H2O
- The ratio of carbon to hydrogen atoms is not the same on both sides of the equation, so option e) is not possible.
Finally, for option b) C2H6:
- There are 2 carbon atoms and 6 hydrogen atoms.
- The balanced equation would be: C2H6 + 7/2O2 → 2CO2 + 3H2O
- The ratio of carbon to hydrogen atoms is the same on both sides of the equation, so option b) is a possibility.
Therefore, the molecular formula that could be the compound described is option b) C2H6.