Question

read the statement.
in your car engine, octane (c₈h₁₈) undergoes a combustion reaction.
what balanced equation showed the products formed?
○ 2c₈h₁₈ + 9o₂ → 18h₂o + 16c
○ c₈h₁₈ → 8c + 9h₂
○ 2c₈h₁₈ + 25o₂ → 18h₂o + 16co₂
○ c₈h₁₈ + 8o₂ → 9h₂ + 8co₂

Explanation:

Step1: Analyze combustion reaction products

In a complete combustion of a hydrocarbon (like octane \(C_8H_{18}\)), the products are carbon dioxide (\(CO_2\)) and water (\(H_2O\)). So we can eliminate the equations that produce \(C\) (elemental carbon) or \(H_2\) (hydrogen gas) as main products. The first equation \(2C_8H_{18}+9O_2
ightarrow18H_2O + 16C\) and the second equation \(C_8H_{18}
ightarrow8C + 9H_2\) and the fourth equation \(C_8H_{18}+8O_2
ightarrow9H_2+8CO_2\) are incorrect based on the nature of complete combustion.

Step2: Check atom - balance

For the equation \(2C_8H_{18}+25O_2
ightarrow18H_2O + 16CO_2\):

• Carbon atoms:

On the left - hand side, in \(2C_8H_{18}\), the number of carbon atoms is \(2\times8 = 16\). On the right - hand side, in \(16CO_2\), the number of carbon atoms is \(16\times1=16\).

• Hydrogen atoms:

On the left - hand side, in \(2C_8H_{18}\), the number of hydrogen atoms is \(2\times18 = 36\). On the right - hand side, in \(18H_2O\), the number of hydrogen atoms is \(18\times2=36\).

• Oxygen atoms:

On the left - hand side, in \(25O_2\), the number of oxygen atoms is \(25\times2=50\). On the right - hand side, in \(18H_2O\) there are \(18\times1 = 18\) oxygen atoms and in \(16CO_2\) there are \(16\times2=32\) oxygen atoms. The total number of oxygen atoms on the right - hand side is \(18 + 32=50\).

Answer:

\(2C_8H_{18}+25O_2
ightarrow18H_2O + 16CO_2\)