How do you balance CH3OH + O2 -- CO2 + H2O?

2 Answers
Oct 30, 2016

The balanced equation is 2"CH"_3"OH" + 3"O"_2 → 2"CO"_2 + 4"H"_2"O"2CH3OH+3O22CO2+4H2O

Explanation:

You follow a systematic procedure to balance the equation.

Start with the unbalanced equation:

"CH"_3"OH" + "O"_2 → "CO"_2 + "H"_2"O"CH3OH+O2CO2+H2O

A method that often works is first to balance everything other than "O"O and "H"H, then balance "O"O, and finally balance "H"H.

Another useful procedure is to start with what looks like the most complicated formula.

The most complicated formula looks like "CH"_3"OH"CH3OH. We put a 1 in front of it to remind ourselves that the number is now fixed.

We start with

color(red)(1)"CH"_3"OH" + "O"_2 → "CO"_2 + "H"_2"O"1CH3OH+O2CO2+H2O

Balance "C"C:

We have "1 C"1 C on the left, so we need "1 C"1 C on the right. We put a 1 in front of the "CO"_2CO2.

color(red)(1)"CH"_3"OH" + "O"_2 → color(blue)(1)"CO"_2 + "H"_2"O"1CH3OH+O21CO2+H2O

Balance "H"H:

We can't balance "O"O because we have two oxygen-containing molecules without coefficients. ∴ Let's balance "H"H instead.

We have "4 H"4 H on the left, so we need "4 H"4 H on the right. There are already "2 H"2 H atoms on the right. We must put a 2 in front of the "H"_2"O"H2O.

color(red)(1)"CH"_3"OH" + "O"_2 → color(blue)(1)"CO"_2 + color(orange)(2)"H"_2"O"1CH3OH+O21CO2+2H2O

Balance "O"O:

We have fixed "4 O"4 O on the right and "1 O"1 O on the left. We need "3 O"3 O on the left.

Uh, oh! Fractions!

We start over, this time doubling all the coefficients.

color(red)(2)"CH"_3"OH" + "O"_2 → color(blue)(2)"CO"_2 + color(orange)(4)"H"_2"O"2CH3OH+O22CO2+4H2O

Now we can balance "O"O by putting a 3 in front of "O"_2O2

color(red)(2)"CH"_3"OH" + color(purple)(3)"O"_2 → color(blue)(2)"CO"_2 + color(orange)(4)"H"_2"O"2CH3OH+3O22CO2+4H2O

Every formula now has a coefficient. We should have a balanced equation.

Let's check.

"Atom" color(white)(m)"lhs"color(white)(m)"rhs"Atommlhsmrhs
color(white)(m)"C"color(white)(mml)2color(white)(mm)2mCmml2mm2
color(white)(m)"H"color(white)(mml)8color(white)(mm)8mHmml8mm8
color(white)(m)"O"color(white)(mml)8color(white)(mm)8mOmml8mm8

All atoms balance. The balanced equation is

2"CH"_3"OH" + 3"O"_2 → 2"CO"_2 + 4"H"_2"O"2CH3OH+3O22CO2+4H2O

Oct 31, 2016

2CH_3OH2CH3OH + 3O_2+3O2 rarr 2CO_2 +4H_2O2CO2+4H2O .

Explanation:

  • First try to balance atoms other than O and H. So first balance the C atoms.
    2CH_3OH2CH3OH + O_2+O2 rarr 2CO_2 +H_2O2CO2+H2O .
  • Then balance the H atoms, as no. of H atoms is less than no. of O atoms.
    2CH_3OH2CH3OH + O_2+O2 rarr 2CO_2 +4H_2O2CO2+4H2O .
  • Now, balance the remaining O atoms.
    2CH_3OH2CH3OH +3 O_2+3O2 rarr 2CO_2 +4H_2O2CO2+4H2O .

Now, check that the no. of all individual atoms in L.H.S and R.H.S are equal.