Question

Assign oxidation numbers to the underlined elements in each of the following species: 

1. \(NaH_2\underline PO_4\) 
2. \(NaH\underline SO_4\) 
3. \(H_4\underline P_2O_7\) 
4. \(K_2\underline {Mn}O_4\) 
5. \(Ca\underline O_2\) 
6. \(Na\underline BH_4\) 
7. \(H_2\underline S_2O_7\) 
8. \(KAl(\underline SO_4)_2.12 H_2O\)

Answer 1

Below are the step-by-step calculations for oxidation numbers of the underlined elements using standard rules: alkali metals (+1), H (+1 except in hydrides -1), O (-2 except peroxides -1), etc. Neutral compounds sum to 0.[web:1][web:4][page:0][web:6]

NaH₂PO₄ (P underlined)

\( +1 + 2(+1) + x + 4(-2) = 0 \)

\( x = +5 \)

P: +5

 

NaHSO₄ (S underlined)

\( +1 + (+1) + x + 4(-2) = 0 \)

\( x = +6 \)

S: +6

 

H₄P₂O₇ (P underlined)

\( 4(+1) + 2x + 7(-2) = 0 \)

\( x = +5 \)

P: +5

 

K₂MnO₄ (Mn underlined)

\( 2(+1) + x + 4(-2) = 0 \)

\( x = +6 \)

Mn: +6

 

CaO₂ (O underlined)

\( +2 + 2x = 0 \) (peroxide)

\( x = -1 \)

O: -1

[web:11][page:0][web:6]

NaBH₄ (B underlined)

\( +1 + x + 4(-1) = 0 \) (hydride)

\( x = +3 \)

B: +3

 

H₂S₂O₇ (S underlined)

\( 2(+1) + 2x + 7(-2) = 0 \)

\( x = +6 \)

S: +6

 

KAl(SO₄)₂·12H₂O (S underlined)

Ignore water: \( +1 + (+3) + 2x + 8(-2) = 0 \)

\( x = +6 \)

S: +6