Balance the following equations;
b) C4H9SH(g) + O2(g)
--heat--> CO2(g) + H2O(g) + SO2(g)
Answer
This equation appears to be a little more complicated that
the formation equations we were discussing. But if maintain
control we'll see these are not that difficult. It is all in the
approach.
To balance combustion reactions always balance the element
oxygen, O2, last. If we do that we need to balance
carbon, hydrogen and sulfur first, we'll do that beginning with
carbon.
C4H9SH(g) + O2(g)
--heat--> CO2(g) + H2O(g) + SO2(g)
There are four carbon atoms (C4H9SH)
on the left side and one carbon atom (CO2) on the
right side. Changing the coefficient before CO2 will
balance the carbon atoms. The new coefficent is '4'.
C4H9SH(g) + O2(g)
--heat--> 4CO2(g) + H2O(g)
+ SO2(g)
Now hydrogen...let's see ten hydrogen atoms on
the left (C4H9SH) and only two on the right
(H2O). So I'll need to change the coefficient before H2O
from '1' to '5' and that will balance the hydrogen atoms.
C4H9SH(g) + O2(g)
--heat--> 4CO2(g) + 5H2O(g) + SO2(g)
To balance sulfur, there is one sulfur atom on
the left and , hey there is also one sulfur atom on the right.
Alright! the sulfur is balanced!
Now we'll balance the oxygen atoms. There are
two oxygen atoms (O2) on the left and fifteen oxygen
atoms on the right (4CO2
+ 5H2O + SO2).
So we need fifteen oxygen atoms on the left. But on the left
oxygen only comes in pairs. How do we get fifteen oxygen atoms,
we can get fourteen by placing a '7' in front of O2,
or we can get sixteen by placing a coefficent of '8' in front of
O2. How do we get fifteen? We can use a coefficient of
7.5, or 15/2 (fifteen halves).
C4H9SH(g) + 15/2O2(g) --heat--> 4CO2(g) + 5H2O(g)
+ SO2(g)
But we do not want fractional coefficients, so
we'll multiply the complete equation by 2!
2 (C4H9SH(g) + 15/2O2(g)
--heat--> 4CO2(g) + 5H2O(g) + SO2(g))
and we get,
2C4H9SH(g) + 15O2(g)
--heat--> 8CO2(g) + 10H2O(g) + 2SO2(g))
Now the equation is balanced.