1. ⇒ (MHT CET 2023 11th May Morning Shift )

Oxidation state of manganese in potassium permanganate is:

A. +3

B. +7

C. +5

D. +1

Correct Option is (B)

Oxidation number of $K = + 1$

Oxidation number of $O = - 2$

${KMnO}_{4}$ is a neutral molecule.

$∴$ Sum of the oxidation number of all atoms $= 0$

Oxidation number of $K +$ Oxidation number of $Mn + 4 \times ($ Oxidation number of $O) = 0$

$(+ 1) + ($ Oxidation number of $Mn) + 4 \times (- 2) = 0$

$1 + ($ Oxidation number of $Mn) = + 8$

$∴$ Oxidation number of $Mn = + 7$

2. ⇒ (MHT CET 2023 9th May Evening Shift )

What is the stock notation of Manganese dioxide?

A. $Mn (I) O_{2}$

B. $Mn (II) O_{2}$

C. $Mn (III) O_{2}$

D. $Mn (IV) O_{2}$

Correct Option is (D)

The oxidation state of $Mn$ in manganese dioxide $({MnO}_{2})$ is +4 . Hence, the stock notation is $Mn (IV) O_{2}$

3. ⇒ (MHT CET 2023 9th May Morning Shift )

What are different possible oxidation states exhibited by scandium?

A. $+ 4$

B. $+ 5$

C. $+ 4, + 5$

D. $+ 2, + 3$

Correct Option is (D)

Scandium typically exhibits a $+ 3$ oxidation state. This is because it has an electronic configuration of $[Ar] 3 d^{1} 4 s^{2}$ , and it typically loses the three outer electrons to achieve a noble gas configuration. While a $+ 2$ oxidation state is theoretically possible, it is not commonly observed. Scandium does not commonly exhibit $+ 4$ or $+ 5$ oxidation states.

Thus, the correct answer to the question is :

Option D : $+ 2, + 3$

⇒Transition and Inner Transition Elements