To balance the reaction of methane (CH4) and oxygen (O2) producing carbon dioxide (CO2) and water (H2O), we start with the unbalanced equation:
CH4 + O2 → CO2 + H2O
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On the left, we have:
- 1 carbon (C)
- 4 hydrogens (H)
- The number of oxygens (O) is what we need to determine.
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On the right side:
- From CO2, we have 1 carbon and 2 oxygens.
- From H2O, we have 2 hydrogens and 1 oxygen.
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So now counting the products:
- For carbon, we have 1 from CO2, which matches the 1 from CH4.
- For hydrogen, we have 2 from H2O, so to balance the 4 hydrogens from CH4, we need 2 H2O:
- This means we adjust the number of water molecules: CH4 + O2 → CO2 + 2 H2O
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Now recounting:
- We still have 1 carbon.
- Now we have 4 hydrogens (2 H2O) from the products.
- For oxygen, we now have 2 from CO2 and 2 from 2 H2O, giving us a total of 4 oxygens.
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On the left side, we need to find how many O2 are required to get that 4 oxygens. Since each O2 has 2 oxygens:
- We need 4 Oxygens total, which means we need 2 O2 molecules since 2 O2 = 4 O.
The balanced equation is: CH4 + 2 O2 → CO2 + 2 H2O
Thus, the answer is two (2 O2 molecules are necessary to complete the reaction).