Сr(NO³)3
w(cr)
w(N)
W(O)

Сябки!!!

Mr(Сr(NO3)3) = 52+3*14+9*16 = 238W(Cr) = 52/238=0.22=22 %W(N) = 42/238 = 0.18=18%W(O) = 144/238 = 0.6 =60%