Ответ:

1) w(Mg) = 24 / 24 + 35,5*2 = 24/95 = 0,243 = 24,3%

  w(Cl) = 35.5*2 / 24 + 35,5*2 = 71/95 = 0,747 = 74,7%

  M(Mg) : M(Cl2) = 24 : 71 = 1 : 2.95

2) w(Na) = 23 / 23 + 80 = 23/103 = 0.223 = 22.3%

   w(Br) = 80 / 23 + 80 = 80/103 = 0.777 = 77.7%

    M(Na) : M(Br) = 23 : 80 = 1 : 3.48 или 0.2875 : 1

3) w(P) = 31 / 31 + 3*1 = 31/34 = 0.912 = 91.2%

   w(H) = 3*1 / 34 = 3/34 = 0.088 = 8.8%

    M(P) : M(H) = 31 : 3 = 10.333 : 1

4) w(Cr) = 52 / 52 + 16*3 = 52/100 = 0.52 = 52%

   w(O) = 48 / 52 + 16*3 = 48/100 = 0.48 = 48%

   M(Cr) : M(O) = 52 : 48 = 1.0833 : 1