# When carbon burns in limited oxygen gas to form carbon monoxide gas, is the equation `C + 1/2 O_2 -> CO` ? The reaction above is called synthesis since two different substances combined to form one new substance. Its chemical equation has a form:

`A + B -> AB`

So when a carbon reacts with oxygen to form carbon monoxide, its equation is:

`C + O_2 -> CO`

However, this is an...

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The reaction above is called synthesis since two different substances combined to form one new substance. Its chemical equation has a form:

`A + B -> AB`

So when a carbon reacts with oxygen to form carbon monoxide, its equation is:

`C + O_2 -> CO`

However, this is an unbalanced equation.

Note that we need to express all chemical reactions in a balanced equation. To do so, count the number of atoms of each element at the left sides as well as the elements at the right side.

At the left side, there are:

1 atom of Carbon and 2 atoms of oxygen

And at the righg side, there are:

1 atom of Carbon and 1 atom of oxygen

To have 2 atoms of oxygen at the right side, multiply CO with 2.

The equation becomes:

`C + O_2 -> 2CO`

Still we have unbalanced equation since at the left side,there are:

1 atom of Carbon and 2 atoms of oxygen

And at the right side, there are

2 atoms of carbon and 2 atoms of oxygen

So to have equal number of carbon, multiply the C at the right side by 2.

`2C + O_2-> 2CO`

So, both sides have:

2 atoms of carbon and 2 atoms of oxygen.

Since number of atoms of each element at the left side is the same with the right side, the chemical equation is now balanced.

Hence, the chemical equation when carbon reacts with oxygen is `2C + O_2 ->2CO` .

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