combustion: C2H6(g)+O2(g)⟶Δ
The Correct Answer and Explanation is:
Balanced Combustion Reaction:
The complete combustion of ethane gas (C₂H₆) in the presence of oxygen (O₂) produces carbon dioxide (CO₂) and water (H₂O):
C₂H₆(g) + O₂(g) ⟶ CO₂(g) + H₂O(g)
To balance this equation, follow these steps:
- Balance carbon (C) atoms first:
Ethane (C₂H₆) has 2 carbon atoms, so you need 2 CO₂ molecules.
C₂H₆ + O₂ ⟶ 2CO₂ + H₂O - Balance hydrogen (H) atoms next:
Ethane has 6 hydrogen atoms, so you need 3 H₂O molecules.
C₂H₆ + O₂ ⟶ 2CO₂ + 3H₂O - Balance oxygen (O) atoms last:
On the right side, you have 2 CO₂ and 3 H₂O, which equals 4 + 3 = 7 oxygen atoms.
On the left side, each O₂ molecule contains 2 oxygen atoms. To get 7, use 3.5 O₂.
C₂H₆ + 3.5O₂ ⟶ 2CO₂ + 3H₂O - To remove the fraction, multiply all coefficients by 2:
2C₂H₆ + 7O₂ ⟶ 4CO₂ + 6H₂O
Explanation
Combustion is a chemical reaction in which a substance reacts rapidly with oxygen, releasing energy in the form of heat and light. In the case of hydrocarbons like ethane (C₂H₆), combustion results in the formation of carbon dioxide and water if enough oxygen is present. This is called complete combustion.
The general formula for the complete combustion of a hydrocarbon is:
Hydrocarbon + O₂ → CO₂ + H₂O
Ethane has 2 carbon atoms and 6 hydrogen atoms. To ensure the law of conservation of mass is followed, each type of atom must be balanced on both sides of the equation. Two carbon atoms in ethane produce two carbon dioxide molecules. Six hydrogen atoms form three water molecules, since each water molecule has two hydrogen atoms. Then, you count the oxygen atoms needed on the product side: 4 from carbon dioxide and 3 from water, totaling 7 oxygen atoms. To get 7 oxygen atoms from O₂ molecules, you need 3.5 O₂. But chemical equations should not have fractional coefficients, so you multiply the entire equation by 2 to eliminate the half-molecule. This gives the final balanced equation:
2C₂H₆ + 7O₂ ⟶ 4CO₂ + 6H₂O
This reaction is exothermic, meaning it releases energy. Combustion reactions like this are essential in applications such as heating, cooking, and powering engines. Complete combustion also helps minimize the production of pollutants like carbon monoxide.
