To determine which chemical equation correctly represents the combustion of ethanol ([tex]$CH_3CH_2OH$[/tex]) in excess oxygen, let's carefully analyze each given equation step-by-step.
1. Combustion Reaction Overview:
The general form of the combustion reaction for an alcohol (like ethanol, [tex]$CH_3CH_2OH$[/tex]) with oxygen ([tex]$O_2$[/tex]) involves converting ethanol and oxygen into carbon dioxide ([tex]$CO_2$[/tex]) and water ([tex]$H_2O$[/tex]).
2. Balanced Chemical Equation:
The balanced equation for the combustion of ethanol in excess oxygen is:
[tex]\[
C_2H_5OH + 3 O_2 \rightarrow 2 CO_2 + 3 H_2O
\][/tex]
To balance this equation:
- Ethanol ([tex]$CH_3CH_2OH$[/tex]) has 2 carbons, 6 hydrogens, and 1 oxygen.
- The products should also have 2 carbons (which will come from [tex]$CO_2$[/tex]), 6 hydrogens (which will come from [tex]$H_2O$[/tex]), and the appropriate amount of oxygen from both products.
3. Analyzing the Given Options:
Let's check each given equation to see if it matches the balanced equation:
- Option A: [tex]$2 CH_3CH_2OH + 3 O_2 \rightarrow 4 CO_2 + 6 H_2$[/tex]
- This does not match because the products should include [tex]$H_2O$[/tex] instead of [tex]$H_2$[/tex].
- Option B: [tex]$2 CH_3CH_2OH + 4 O_2 \rightarrow 4 CO + 6 H_2O$[/tex]
- This does not match because carbon monoxide ([tex]$CO$[/tex]) is not a product of complete combustion; we should have carbon dioxide ([tex]$CO_2$[/tex]).
- Option C: [tex]$CH_3CH_2OH + 3 O_2 \rightarrow 2 CO_2 + 3 H_2O$[/tex]
- This equation matches the balanced equation we derived. It correctly shows [tex]$1$[/tex] ethanol molecule reacting with [tex]$3$[/tex] oxygen molecules to produce [tex]$2$[/tex] carbon dioxide molecules and [tex]$3$[/tex] water molecules.
- Option D: [tex]$2 CH_3CH_2OH + 9 O_2 \rightarrow 4 CO_2 + 6 H_2O_2$[/tex]
- This does not match because [tex]$H_2O_2$[/tex] (hydrogen peroxide) is not a product of the combustion of ethanol.
4. Correct Answer:
After reviewing each option, we see that the correct chemical equation for the combustion of ethanol is provided in Option C.
Therefore, the correct answer is:
[tex]\[ \text{C. } CH_3CH_2OH + 3 O_2 \rightarrow 2 CO_2 + 3 H_2O \][/tex]
