Масова частка K2 Cr2 O7
Mr(K2Cr2O7) = 39*2 + 52*2 + 16*7 = 294 W(K) = Ar(K) *n / Mr(K2Cr2O7) *100% = 39*2 / 294 *100% = 26,5% W(Cr) = Ar(Cr) * n / Mr(K2Cr2O7) *100% = 52*2 / 294 *100% =35,4% W(O) = Ar(O) * n / Mr(K2Cr2O7) *100% = 16*7 / 294 *100% = 39%