4P + 5O2 = 2P2O5
1) m(NaOH)=m(раствора)*w(NaOH)=200*0.2/100=0.4 г NaOH
m(NH4OH) = n * M
n (NH4OH) = m/ M = 250/ 14 +4+16+1 = 250/35 = 7, 1 моль