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

`(a) P " in " NaH_(2)PO_(4)`
`overset(+1)Na overset(+1)H_(2)overset(x)Poverset(-2)P_(4)`
`(+1)+2(+1)+x+4(-2)=0`
`x+3-8=0 or x=+5.`
`(b)S " in " NaHSO_(4)`
`overset(+1)Naoverset(+1)Hoverset(x)Soverset(-2)O_(4)`
`(+1)+(+1)+x+4(-2)=0`
`x-6=0 or x=+6`
`(c) P " in " H_(4)P_(2)O_(7)`
`overset(+1)H_(4)overset(x)P_(2)overset(-2)O_(7)`
`4(+1)+2x+7(-2)=0`
`2x-10=0 or x=+5`
`(d) Mn " in " K_(2)MnO_(4)`
`overset)(+1)K_(2)overset(x)Mnoverset(-2)O_(4)`
`2(+1)+x+4(-2)=0`
`x-6=0 or x=+6`
`(e)O" in "CaO_(2)`
`overset(+2)CAoverset(x)O_(2)`
`(+2)+2(x)=0 or x=-1`
`(f) B"in" NaBH_(4)`
`overset(+1)Naoverset(x)Boverset(-1)H_(4)`
`+1+x+4(-1)=0`
`x-3=0 or x=+3`
`(g)S " in " H_(2)S_(2)O_(7)`
`overset(+1)Hoverset(x)S_(2)overset(-2)O_(7)`
`2(+1)+2(+x)+7(-2)=0`
`2x-12=0 or x=+6`
`S " in " KAI (SO_(4)_(2)).12 H_(2)O`
`overset(+1)Koverset(+3)AIoverset(x-2)(SO_(4))_(2)12(H_(2))O`
`+1+3+2x+8(-2)+120(0)=0`
`2x-12=0 or x=+6`