Question

A mixture containing 10 mL of a nitrogen oxide and 30 ml of hydrogen reacts completely to form 10 mL of nitrogen. What is the formula for the nitrogen oxide?

Answer 1

The molecular formula of the compound is `"N"_2"O"_3`.

Explanation:

Step 1. Summarize the information

`color(white)(l)"N"_x"O"_y +color(white)(ll) "H"_2 → color(white)(m)"N"_2 + "H"_2"O"`
`"10 mL"color(white)(ml)"30 mL"color(white)(m)"10 mL"`

Step 2. Assume that the reaction involves 1 mol of the compound

Then the partially balanced equation is

`"1N"_x"O"_y +"3H"_2 → "1N"_2 + "H"_2"O"`

Step 3. Balance `"N"`

We have 2 atoms of `"N"` on the right, so we need 2 atoms of `"N"` on the left.

∴ `x= 2` and

`"N"_2"O"_y + "3H"_2 → "N"_2 + "H"_2"O"`

Step 4. Balance `"H"`

We have 6 `"H"` on the left, so we need 6 `"H"` on the right.

Put a 3 in front of `"H"_2"O"`.

`"N"_2"O"_y + "3H"_2 → "N"_2 + "3H"_2"O"`

Step 5. Balance `"O"`.

We have 3 `"O"` on the right, so we need 3 `"O"` on the left.

∴ `y = 3` and

`"N"_2"O"_3 + "3H"_2 → "N"_2 + "3H"_2"O"`

The formula of the compound is `"N"_2"O"_3`.