Calculate the volume of nitrogen that will be produced at S.T.P from the decomposition of 9.6g of ammonium dioxonitrate 3?

Answer 1

Did you mean NH4NO2. What you wrote is not a correct IUPAC name for NH4NO2 but I'll play the game.
NH4NO2 ==> N2 + 2H2O
mols NH4NO2 = 9.6/molar mass NH4NO2.
Then mols NH4NO2 = mols N2 produced.
Each mol N2 @ STP will occupy 22.4 L
Post your work if you get stuck.