P2O5(2*31/142)*100%=43.66%五氧化二磷中磷的质量分数是43.66%
P2O5中磷元素的质量分数：31*2/(31*2+16*5)*100%=43.662%
P2O5 31*2/(31*2+16*5) *100%=43.7%
(62/142)×100%≈43.67%
