Hey there!
According to the stoichiometry of the reaction:
4 NH3+ 5 O2 -> 4 NO + 6 H2O
4 moles of NO react with 6 moles of H2O so:
4 moles NO --------------- 6 moles H2O
moles NO ------------------- 4.00 moles H2O
moles NO = 4.00 * 4 / 6
moles NO = 16 / 6
=> 4.0 moles of NO
Hope that helps!
