What is the balanced equation of SO2 + O2 = SO3?

1 Answer
May 26, 2014

The balanced equation is "2SO"_2 + "O"_2 → "2SO"_3.

Explanation:

You follow a systematic procedure to balance the equation.

Start with the unbalanced equation:

"SO"_2 + "O"_2 → "SO"_3

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

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

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

"SO"_2 + "O"_2 → color(red)(1) "SO"_3

Balance "S":

We have "1 S" on the right, so we need "1 S" on the left. We put a 1 in front of the "SO"_2.

color(blue)(1) "SO"_2 + "O"_2 → color(red)(1) "SO"_3

Balance "O":

We have "3 O" on the right, so we need "3 O" on the left. There are already "4 O" atoms on the left. We must put a ½ in front of the "O"_2.

Most instructors don't allow fractions in balanced chemical equations, because you can't have a fraction of an atom or a molecule.

To get rid of the fractions, you multiply all the coefficients by 2 and get

color(blue)(2) "SO"_2 + "O"_2 → color(red)(2) "SO"_3

Now you can balance the equation by putting a 1 in front of the "O"_2.

color(blue)(2) "SO"_2 + color(orange)(1) "O"_2 → color(red)(1) "SO"_3

We should now have a balanced equation.

Check to make sure:

bb"Atom"color(white)(m)bb "Left hand side"color(white)(m) bb"Right hand side"
stackrel(————————————————)(color(white)(ml)"S"color(white)(mmmmmm) 2color(white)(mmmmmmmll) 2)
color(white)(ml)"O"color(white)(mmmmmll) 6color(white)(mmmmmmmll) 6

The balanced equation is

"2SO"_2 + "O"_2 → "2SO"_3