Help with balancing equations?

Question

sleepyjess · Answer

$CH_3CH_2OH + O_2~ \rightarrow~ CO_2 + H_2O$

sleepyjess · Answer

@Abhisar

abhisar · Answer

First of all rewrite the equation as

$\sf C_2H_6O+O_2 \rightarrow CO_2+H_2O$

Now start balancing it

abhisar · Answer

Balance the number of oxygen on both the sides first

sleepyjess · Answer

Isn't the oxygen already the same on both sides?

abhisar · Answer

Oh yes, balance carbon first..

sleepyjess · Answer

$C_2O_2+H_2O$?

abhisar · Answer

Okay, now lesson no.1....You can not add numbers as subscript. You can only change coefficients like 2C, 3C and not $\sf C_2~or~C_3$...getting it?

sleepyjess · Answer

Ok, so $2CO_2$?

abhisar · Answer

Yes, lets write the new equation

$\sf C_2H_6O+O_2 \rightarrow \color{red}{2}CO_2+H_2O$

Now lets balance the number of hydrogens. On left hand side it is 6 while on right hand side it's only 2. What will you do ?

sleepyjess · Answer

Make it $\sf 3H_2O$?

abhisar · Answer

Correct!
Yes, lets write the new equation

$\sf C_2H_6O+O_2 \rightarrow \color{red}{2}CO_2+\color{blue}{3}H_2O$

Now finally let's balance the number of oxygen.How many oxygen are there in right hand side?

sleepyjess · Answer

there are 9 oxygens on the right

abhisar · Answer

How?

sleepyjess · Answer

whoops miscounted, 7 oxygen
4 in $\sf 2CO_2$ and 3 in $\sf 3H_2O$

abhisar · Answer

$\huge \checkmark$
Now what will you do to balance it?

abhisar · Answer

because there are only 3 on left hand side.

abhisar · Answer

Remember anything you do but do not disturb counts of other elements....

sleepyjess · Answer

$\sf C_2H_6O+3O_2~\rightarrow~2CO_2+3H_2O$

jhannybean · Answer

One thing to note for combustion reactions:

1. balance carbons first, this will help balance the hydrogens right way
2. Balance the hydrogens, you'll be left with an odd number of oxygens (most times)
3. IAfter the Carbons and Hydrogens are balanced, I like to balance the left hand side of the equation for the Oxygens, and work going towards the right.

abhisar · Answer

$\huge \checkmark$

sleepyjess · Answer

YAY!

abhisar · Answer

Well done! ^_^

abhisar · Answer

And note what jhanny said....

sleepyjess · Answer

Can you help me with one more?

abhisar · Answer

Yep