# What can be the chemical formula of the oxide of the element “X” if it is known

What can be the chemical formula of the oxide of the element “X” if it is known that 3 liters of this gas has a mass of 5.89 g?

Let’s find the amount of substance of an unknown gas:

v (gas) = V (gas) / Vm = 3 / 22.4 (mol).

Let’s find the molar mass of the unknown gas:

M (gas) = m (gas) / v (gas) = 5.89 / (3 / 22.4) = 5.89 * 22.4 / 3 = 44 (g / mol).

This molar mass corresponds to nitric oxide (I) or laughing gas:

M (N2O) = M (N) * 2 + M (O) = 14 * 2 + 16 = 44 (g / mol), i.e. X is nitrogen.

And if dioxides are also taken into account, then carbon monoxide (IV) or carbon dioxide is also suitable:

M (CO2) = M (C) + M (O) * 2 = 12 + 16 * 2 = 44 (g / mol), i.e. X is carbon.

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