Question

Fill in the blank for a stoichiometric iso-octane air mixture. C8H18 + ____ (O2+3.76N2)

6 8 12.5 or 25

Answer 1

Answer: Option 12.5 is the correct answer.

Step-by-step explanation:

The given reaction is as follows.

`C_(8)H_(18) + x(O_(2) + 3.76N_(2)) \rightarrow Products`

As it is a combustion reaction so, nitrogen will not take part in it and hence, it will remain the same on both sides of the reaction.

Also, it is known that in a combustion reaction oxygen reacts with a hydrocarbon and results in the formation of carbon dioxide and water. Therefore, for the above reaction we write the complete reaction equation as follows.

`C_(8)H_(18) + x(O_(2) + 3.76N_(2)) \rightarrow CO_(2) + H_(2)O + 3.76 N_(2)`

or,
`C_(8)H_(18) + xO_(2) \rightarrow CO_(2) + H_(2)O` as nitrogen is not taking part in the reaction.

Number of atoms on reactant side are as follows.

C = 8

H = 18

O = 2

Number of atoms on product side are as follows.

C = 1

O = 3

H = 2

Therefore, to balance this equation we multiply oxygen on reactant side by 12.5. Also, we multiply carbondioxide by 8 and water by 9 on product side. Hence, the complete balanced chemical equation is as follows.

`C_(8)H_(18) + 12.5O_(2) \rightarrow 8CO_(2) + 9H_(2)O`