Question

1. Assign oxidation numbers 

(i) P in NaH₂PO₄

(ii) Mn in KMnO₄ 

(iii) B in NaBH₄ 

(iv) S in H₂SO₄ 

2. Identify the oxidising and reducing agents in the following reaction: 

CuO + H₂ → Cu + H₂O

Answer 1

(i) NaH₂PO₄

Na⁺¹  H₂ ⁺¹  PO₄ ^-2

1+2 + x- 8 = 0 

3 + x – 8 = 0 

x – 5 = 0 

x =+ 5

(ii) K⁺¹  MnO₄ ^-2

1+ x – 8 = 0 

x – 7 = 0 

x = +7

(iii) Na⁺¹ BH₄ ⁺¹

1 + x + 1 × 4 = 0 

x + 5 = 0 

x = -5

(iv) H₂ ⁺¹ SO₄ ^-2

2 + x – 8 = 0 

x – 6 = 0 

x = +6

2.  

CuO is the oxidising agent.

H₂ is the reducing agent.