Question

How many moles of oxygen are required to completely combust 1 mole of propane (C\(_3\)H\(_8\))?

• A. 4 moles
• B. 6 moles
• C. 5 moles
• D. 3 moles

Hint:

Tip: Always balance the combustion of hydrocarbons carefully — follow the pattern C → CO\(_2\), H → H\(_2\)O, then balance O\(_2\).

Answer 1

The Correct Option is C

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:

1. Start with the carbon atoms. We have 3 carbons in propane, so we need 3 CO₂:
   C₃H₈ + O₂ → 3CO₂ + H₂O
2. Next, balance the hydrogen atoms. There are 8 hydrogens in propane, requiring 4 H₂O:
   C₃H₈ + O₂ → 3CO₂ + 4H₂O
3. 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.