Oxidation Number and Oxidation State MCQs

Oxidation state is a fundamental concept in chemistry, especially important in transition metal chemistry, as d-block elements often exhibit a wide range of stable oxidation states. The oxidation state (or number) of an atom in a molecule is typically regarded as the formal charge the atom would have if all the molecules were composed of ions. Oxidation numbers are assigned to atoms in an arbitrary manner to indicate electron transfer in oxidation-reduction reactions. They represent the charges atoms would have if the electrons were distributed according to a specific set of rules. According to IUPAC, the oxidation state of an element is defined as a measure of the degree of oxidation of an atom in a substance.

Which of the following will not be oxidised by O3?

(a) KI
(b) FeSO₄
(c) KMnO₄
(d) K₂MnO₄

Number of moles of K₂Cr₂O₇ reduced by 1 mole of Sn²⁺ is

(a) 1/6
(b) 1/3
(c) 2/3
(d) 1

Number of moles of MnO₄^– required to oxidise one mole of ferrous oxalate completely in the acidic medium will be

(a) 7.5 moles
(b) 0.2 moles
(c) 0.6 moles
(d) 0.4 moles

Which of the following elements does not show disproportionation tendency?

(a) Cl
(b) Br
(c) F
(d) I

The oxidation number of carbon in CH₂Cl₂ is

(a) 0
(b) 2
(c) 3
(d) 5

The oxidation state of each Cl in CaOCl₂ is

(a) 0
(b) +1
(c) -1
(d) +1, -1

What is the oxidation number of chlorine in HClO₄?

(a) +3
(b) +5
(c) +7
(d) +8

What products are expected from the disproportionation reaction of hypochlorous acid?

(a) HCl and Cl₂O
(b) HCl and HClO₃
(c) HClO3 and Cl2O
(d) HClO₂ and HClO₄

The products formed when an aqueous solution of NaBr is electrolysed in a cell having inert electrodes are

(a) Na and Br₂
(b) Na and O₂
(c) H₂, Br₂, NaOH
(d) H₂ and O₂

The oxidation state of chromium in the final product formed by the reaction between KI and acidified potassium dichromate solution is

(a) +4
(b) +6
(c) +2
(d) +3