Đáp án + giải thích các bước giải:

`a,`

`M_{Fe(NO_{3})_{2}} = 56 + (14 + 16.3).2 = 180` amu

`%Fe = 56/180 .100 = 31,11%`

`%N = (14.2)/180 . 100 = 15,56%`

`%O = 100% - 31,11% - 15,56% = 53,33%`

___________________________________________

`M_{Fe(NO_{3})_{3}} = 56 + (14 + 16.3).3 = 242` amu

`%Fe = 56/242 . 100 = 23,14%`

`%N = (14.2)/242 . 100 = 11,57%`

`%O = 100% - 23,14% - 11,57% = 65,29%`

==============================

`b,`

`M_{NO} = 14 + 16 = 30` amu

`%N = 14/30 . 100 = 46,67%`

`%O = 100% - 46,67% = 53,33%`

_______________________________________

`M_{NO_{2}} = 14 + 16.2 = 46` amu

`%N = 14/46 .100 = 30,43%`

`%O = 100% - 30,43% = 69,57%`

________________________________________

`M_{NaNO_{3}} = 23 + 14 +16.3 = 85` amu

`%Na = 23/85 . 100= 27,06%`

`%N = 14/85 .100 = 16,47%`

`%O = 100% - 27,06% - 16,47% = 56,47%`