Ответ:

Объяснение:

Mr(Rb2CO3) = 85*2 + 12 + 16*3 =230

W(Rb) = Ar(Rb) *n / Mr(Rb2CO3)  *100% = 85*2 / 230  *100% =74%

W(C) = Ar(C) *n / Mr(Rb2CO3)  *100% = 12*1 / 230  *100% =5%

W(O) = Ar(O) *n / Mr(Rb2CO3)  *100% = 16*3 / 230  *100% = 21%