Two volumes of an oxide of nitrogen decomposed in the presence of a heated catalyst to form two volumes of nitrogen gas and one volume of oxygen gas, all volumes measured at the same conditions of temperature and pressure - Leaving Cert Chemistry - Question g - 2021

To determine the formula of the nitrogen oxide, we can start by noting the reaction as follows:

$2 \text{NO}_x \xrightarrow[]{\text{catalyst}} 2 \text{N}_2 + \text{O}_2$

From the information given, we deduce that 2 volumes of the nitrogen oxide decompose into 2 volumes of nitrogen (N₂) and 1 volume of oxygen (O₂). This indicates that for every 2 moles of nitrogen oxide, we get 2 moles of nitrogen gas and 1 mole of oxygen gas.

To find the nitrogen oxide formula, let’s establish a stoichiometric relationship:

• The nitrogen oxide decomposes to give twice as much nitrogen gas, leading us to understand that the oxide likely has a ratio of nitrogen to oxygen.

Thus, employing the law of conservation of mass and the known volume ratios, we can establish the formula:

• If we assume the formula of the nitrogen oxide is NₓOᵧ, and from the reaction we see that there must be 1 oxygen for every 2 nitrogen:

We conclude that the simplest whole number ratio is:

$x : y = 2 : 1$

Thus, the probable formula is N₂O.