Question

Balance the equation ? C4H10 (g) + ? O2 (g) → ? CO2 (g) + ? H2O (g), using the smallest possible integers. What is the coefficient of CO2?

Answer 1

See the explanation

Explanation:

The balanced equation for this is

`2C_4H_10+13O_2rarr8CO_2+10H_2O`

The coefficient of `CO_2` is `8`.

Answer 2

`C_4H_10(g) + 13/2O_2(g)rarr4CO_2(g) + 5H_2O(l)`

Explanation:

The usual rigmarole is to assume complete combustion, and balance the carbons as carbons as carbon dioxide, balance the hydrogens as water, and AND then balance the oxygens....i.e..

`C_4H_10(g) + 13/2O_2(g) rarr4CO_2(g) + 5H_2O(l)`

But you wanted whole number coefficients...so the entire equation is DOUBLED...

`2C_4H_10(g) + 13O_2(g) rarr8CO_2(g) + 10H_2O(l)`

Mass and charge are balanced as required. You can get very proficient at doing this sort of thing...try it out for benzene...`C_6H_6`...and then try it out assuming that SOME `CO` and some `C` is produced during the combustion.

This is taken from a prior answer and shows the combustion of other hydrocarbons...

....there is ethane, `C_2H_6`...which combusts according to the equation...

`C_2H_6(g) +7/2O_2rarr 2CO_2(g)+3H_2O(l)+Delta_1`

And ethylene, with the one degree of saturation....

`H_2C=CH_2(g) +3O_2rarr 2CO_2(g)+2H_2O(l)+Delta_2`

And acetylene, with the two degrees of saturation....

`HC-=CH(g) +5/2O_2rarr 2CO_2(g)+H_2O(l)+Delta_3`

The usual rigmarole in these combustion equations (which are in fact redox equations!) is to (i) balance the carbons as carbon dioxide, (ii) balance the hydrogens as water, and then (iii) balance the oxygens.

A priori, could you predict the order of heat evolved in the reaction? That is, is `Delta_3>Delta_2` etc... why or why not?