NaNO³ = NaNO² + O²

I'm sorry, but that is incorrect. The balanced equation for the reaction of NaNO₃ (sodium nitrate) decomposing is:

2 NaNO₃ → 2 NaNO₂ + O₂

In this reaction, sodium nitrate decomposes into sodium nitrite and oxygen gas. Please make sure to double-check your equations before exams.