Question:
How many moles of oxygen are required to completely combust 1 mole of propane (C\(_3\)H\(_8\))?
How many moles of oxygen are required to completely combust 1 mole of propane (C\(_3\)H\(_8\))?
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Tip: Always balance the combustion of hydrocarbons carefully — follow the pattern C → CO\(_2\), H → H\(_2\)O, then balance O\(_2\).
Updated On: Jan 13, 2026
- 4 moles
- 6 moles
- 5 moles
- 3 moles
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The Correct Option is C
Approach Solution - 1
To determine the moles of oxygen required for the complete combustion of 1 mole of propane (C\(_3\)H\(_8\)), we must first write the balanced chemical equation for the combustion process. The combustion of propane is represented by:
C\(_3\)H\(_8\) + 5O\(_2\) → 3CO\(_2\) + 4H\(_2\)O
This equation indicates that 1 mole of propane (C\(_3\)H\(_8\)) reacts with 5 moles of oxygen (O\(_2\)) to produce 3 moles of carbon dioxide (CO\(_2\)) and 4 moles of water (H\(_2\)O).
Therefore, 5 moles of oxygen are required to completely combust 1 mole of propane.
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Approach Solution -2
To determine how many moles of oxygen are required to completely combust 1 mole of propane (C3H8), we first need to write the balanced chemical equation for the combustion reaction:
C3H8 + O2 → CO2 + H2O
Let's balance this equation step by step:
- Start with the carbon atoms. We have 3 carbons in propane, so we need 3 CO2:
C3H8 + O2 → 3CO2 + H2O - Next, balance the hydrogen atoms. There are 8 hydrogens in propane, requiring 4 H2O:
C3H8 + O2 → 3CO2 + 4H2O - Finally, balance the oxygen atoms. We have 3 CO2 contributing 6 oxygen atoms and 4 H2O contributing 4 oxygen atoms, for a total of 10 oxygen atoms required from O2. Since each O2 molecule provides 2 oxygen atoms, 5 O2 molecules are needed:
C3H8 + 5O2 → 3CO2 + 4H2O
Therefore, 5 moles of oxygen (O2) are required to completely combust 1 mole of propane (C3H8).
| Substance | Moles in Reaction |
|---|---|
| C3H8 | 1 |
| O2 | 5 |
| CO2 | 3 |
| H2O | 4 |
Thus, the correct answer is 5 moles.
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