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?

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Answer 1 · 2017-06-02T20:31:07

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

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 $"N"_2"O"_3$ .