Assign oxidation number to the underlined elements in each of the following species:
a.`NaH_(2)PO_(4)`
b. `NaHul(S)O_(4)`
c. `H_(4)ul(P_(2))O_(7)`
d. `K_(2)ul(Mn)O_(4)`
e. `ul(Ca)O_(2)`
f. `Naul(B)H_(4)`
g. `H_(2)ul(S_(2))O_(7)`
h. `KAl(ul(S)O_(4))_(2).12H_(2)O`

Explanation

Let the oxidation number of underlined atom be x.
(a) `{:(overset(+1)(Na),overset(+1)(H_2),overset(x)P,overset(+2)O_4):}`
`1(+1) +2(+1) +x+4 (-2) = 0 " ":. x = +5`
Oxidation number of P in `NaH_2PO_4` is +5.
(b) `{:(overset(+1)(H_4),overset(+1)(H),overset(x)S,overset(-2)O_4):}`
`1(+1) +1(+1)+x+4(-2)=0`

`x-6=0 " "x=+6`
(c) `{:(overset(+1)(H_4),overset(x)P_2,overset(-2)O_7):}`
`4(+1)+2(x)+7(-)=0`
`2x -10 = 0 " ":. x=+5`
(d) `{:(overset(+1)(K_2),overset(x)(Mn),overset(-2)O_4):}`
`2(+1)+x+4(-2)=0`
`x-6 =0 " " :. x=+6`
(e) `{:(overset(+2)(Ca),overset(x)O_2):}`
`+2+2(x)=0" ":. x=-1`
(f) `{:(overset(+1)(Na),overset(x)B,overset(-1)H_4):}`
`1(+1)+x+4(-1)=0`
`x-3=0 " ":.x=+3`
(g) `{:(overset(+1)(H_2),overset(x)S_2,overset(-2)O_7):}`
`2(+1) +2(x)+7(-2)=0`
`2x-12 =0 " ":.x=+6`
(h) `overset(+1)(K),overset(+3)(Al),overset(x" "-2)((S" "O_4))_(2).12overset(+1)(H_2)overset(-2)O`
`1(+1)+1(+3)+2x+8(-2)+12(2xx1-2)=0`
`2x-12 =0 " ":. x =+6`