А) Mr (H2SO4) = 2 + 32 + 64 = 98 г/моль
w (H) = 2/98*100% = 2%
w (S) = 32/98*100% = 32,7%
w (O) = 64/98*100% = 65,3%
б) Mr (P2O5) = 62 + 80 = 142 г/моль
w (P) = 62/142*100% = 43,7%
w (O) = 80/142*100% = 56,3%
в) Mr (Zn(NO3)2) = 65 + 28 + 96 = 189 г/моль
w (Zn) = 65/189*100% = 34,4%
w (N) = 28/189*100% = 14,8%
w (O) = 96/189*100% = 50,8%