Chemistry and Chemical Reactivity (9th Edition)

Number of moles of hydrazine: $1000\ g\div 32.05\ g/mol=31.21\ mol$ From stoichiometry: $31.21\ mol$ of oxygen From ideal gas law: $PV=nRT$ $P=31.21\ mol×0.082057\ L.atm/mol.K×(23+273)\ K/450\ L$ $P=1.68\ atm$