the combustion réaction of ethane gas [C2H6(g)

Question

the combustion réaction of ethane gas [C2H6(g)

Answer 1

This is essentially a problem of balancing chemical equations. The first thing to remember in any combustion reaction is that the reaction involves the reaction of an organic compound with O_2. So the first thing we write on the left side of the equation is C₂H₆ + O_2. In a combustion reaction the organic compound undergoes an oxidation, and will form the most oxidized carbon species, i.e. CO_2. In addition, O₂ undergoes reduction to form water. So the overall reaction (eq 1) is:

AC₂H₆ + BO₂ ------> CH₂O + DCO₂ (1)

2O 3O

2C 1C

6H 2H

In this equation we can tally up the atoms on the left side of the reaction, and do the same for the right. We see that the equation is not balanced. Therefore, we must modify the coefficients A,B,C, and D in such a way to honor the law of conservation of mass. A good place (but not the only place) to start is to look at the carbon count for each side of the equation. We can see that a molecule containing 2 carbons on the left side (C₂H₆) is tranformed to a molecule containing 1 carbon on the right (CO₂). Therefore, we can replace D in the equation with 2A (eq 2).

AC₂H₆ + BO₂ ------> CH₂O + 2ACO₂ (2)

Next, substitute an actual number for A (it doesn't matter what number, but simpler is better in all cases) Therefore, let's input A = 1. Our new equation is thus eq 3.

C₂H₆ + BO₂ ------> CH₂O + 2CO₂ (3)

Because we have already assigned the left side of the equation to give 6 H atoms, we must assign C = 1 (eq 4).

C₂H₆ + BO₂ ------> 3H₂O + 2CO₂ (4)

2C 2C

6H 6H

2B O 7O

With this assignment, we can tally the atom count on both sides and infer that 2B = 7, and thus B = 3.5. Then input this number into the equation.

C₂H₆ + 3.5O₂ ------> 3H₂O + 2CO₂ (5)

Conventionally, we only use whole numbers for coefficients when balancing equations. So, the last step is to simply multiply the entire equation by the smallest whole number that gives whole numbers for each coefficient in these case we multiply each coefficient by 2. Our final balanced equation is therefore eq 6.

2C₂H₆ + 7O₂ ------> 6H₂O + 4CO₂ (6)