N2H4 + O2 ===> N2 + 2H2O
Molar mass of N2H4 = 32.0 g/mol
mole of N2H4 = 3.45 g / 32.0 g/mol = 0.107 mol
stochiometric ration between N2H2 and N2 is 1:1
Hence during the reaction 0.107 N2 was released (theoricaly)
Now lets find the practically evolved N2 mol using PV=nRT
n=PV/RT
n= (1 atm * 0.95 L)/ (295 K* 0.082057)
N= 0.0392 mol
Yield= (0.0392/0.107)*100 = 36.68%