Question

1.     Which of the following has the incorrect assignment of oxidation numbers?

a.      Fe₂O₃ (Fe: 2+, O: 2-)

b.     H₂SO₄ (H:1+, S: 6+, O: 2-)

c.      Cr₂O₇^2- (Cr: 6+, O: 2-)

d.     KCl (K: 1+, Cl: 1-)

 

2.     Which of the following has the incorrect assignment of oxidation numbers?

a.      H₂O₂ (H: 1+, O: 2-)

b.     NO₃^– (N: 5+, O: 2-)

c.      NO₂ (N: 4+, O: 2-)

d.     K₃PO₄: (K: 1+, P: 5+, O: 2-)

 

3.    Which of the following has the incorrect assignment of oxidation numbers?

a.      SiO₂ (Si: 4+, O: 2-)

b.     KNO­₂ (K: 1+, N: 3+, O: 2-)

c.      HNO₃ (H: 1+, N: 3+, O: 2-)

d.     NH­₄Cl (N: 3-, H: 1+, Cl: 1-)

Answer 1

Solution:

(1) Which of the following has the incorrect assignment of oxidation numbers?

a) Fe₂O₃ (Fe: 2+, O: 2−) – incorrect. Fe₂O₃ (Fe: 3+, O: 2−) – correct

b) H₂SO₄ (H:1+, S: 6+, O: 2−) – correct

c) Cr₂O₇^2- (Cr: 6+, O: 2−) – correct

d) KCl (K: 1+, Cl: 1−) – correct

Answer (1):

a) Fe₂O₃ (Fe: 2+, O: 2−)

(2) Which of the following has the incorrect assignment of oxidation numbers?

a) H₂O₂ (H: 1+, O: 2−) – incorrect. H₂O₂ (H: 1+, O: 1−) – correct.

b) NO₃^– (N: 5+, O: 2−) – correct

c) NO₂ (N: 4+, O: 2−) – correct

d) K₃PO₄: (K: 1+, P: 5+, O: 2−) – correct

Answer (2):

a) H₂O₂ (H: 1+, O: 2−)

(3) Which of the following has the incorrect assignment of oxidation numbers?

a) SiO₂ (Si: 4+, O: 2−) – correct

b) KNO­₂ (K: 1+, N: 3+, O: 2−) – correct

c) HNO₃ (H: 1+, N: 3+, O: 2−) – incorrect. HNO₃ (H: 1+, N: 5+, O: 2−) – correct.

d) NH­₄Cl (N: 3-, H: 1+, Cl: 1−) – correct

Answer (3):

c) HNO₃ (H: 1+, N: 3+, O: 2−)