Question

1.) A. Which of the following compounds contain an oxygen atom whose oxidation number is not equal to -2? [Select all that apply.]

H2O2, CO2, O2, CH2O, H2O, OF2, O2F2

B. What are the oxidation numbers of the nitrogen and oxygen atoms in the nitrate ion (NO3-)?

Oxygen?

Nitrogen?

Answer 1

Ans. #1. Oxygen is the second most electronegative element in the periodic table.

The oxidation number of O-atom is always -2 except –

I. In peroxides: A compound having a single covalent bond between two O-atoms is called a peroxide. In peroxide, the oxidation number of O-atom is -1, except in O₂F₂ where its oxidation number os +1.

II. In oxides of fluorine. Fluorine is the most electronegative atom in the periodic table. So, it withdraw electrons from O-atom towards itself creating a positive charge on the O-atom. So, in oxides of fluorine, OF₂, the O-atom bears +2 charge.

III. In O₂ molecule, two O-atoms are covalently linked. Since both the atoms have same electronegativity, no net charge appear on any atom.

So, the oxidation number of O-atom in O₂ is zero (0).

So, the correct options are- H₂O₂ and O₂F₂, OF₂, O₂.

#2.