P2o5 Mr(P2O5)=31*2+16*5=142 SO3 Mr(SO3)=32+48=80 CO2 Mr(CO2)=12+32=44 NH3 Mr(Nh3)=14+3=17 FeS2 Mr(FeS2)=56+64=120 CH4 Mr(CH4)=12+4=16 CCl4 Mr(CCl4)=12+35,5*4=154 HCl Mr(HCl)=35,5+1=36,5 SO2 Mr(SO2)=32+32=64 FeCl3 Mr(FeCl3)=56+35,5*3=162,5