A mixture of potassium chlorate, oxalic acid and sulphuric acid is heated. During the

reaction which element undergoes a maximum change in the oxidation number?

1. S

2. H

3. Cl

4. C

The oxidation states of P in H₄P₂O₅, H₄P₂O₆, H₄P₂O₇, are respectively -

Oxidation numbers of P in ${\mathrm{PO}}_4^{3-}$, of S in ${\mathrm{SO}}_4^{2-}$ and that of Cr in ${\mathrm{Cr}}_2{\mathrm{O}}_7^{2-}$ are respectively,

1. +5, +6 and +6                     

2. +3, +6 and +5

3. +5, +3 and +6                     

4. -3, +6 and +6

The number of moles of MnO^-₄ required to oxidise one mole of ferrous oxalate completely in an acidic medium is-

1. 0.6 mole

2. 0.4 mole

3. 7.5 moles

4. 0.2 mole

Which one of the following orders correctly represents the increasing acid strengths of the given acids?

(1) HOCl <HOClO <HOClO₂ < HOClO₃

(2) HOClO <HOCl <HOClO₃ <HOClO₂

(3) HOClO₂ <HOClO₃ <HOClO <HOCl

(4) HOClO₃> HOClO₂ <HOClO <HOCl

What enables HNO₂ to act as both a reducing and an oxidizing agent, in contrast to HNO₃ which only acts as an oxidizing agent?

1. Hybridization of N-atom in HNO₂

2. Maximum oxidation state of N - atom in HNO₂

3. Lower oxidation state of N-atom in HNO₂

4. Higher Electronegativity of N -atom in HNO₃

The valency of Cr in the complex [Cr(H₂O)₄Cl₂]⁺ [MP PMT 2000]

(1) 1

(2) 3

(3) 5

(4) 6

In the conversion ${\text{Br}}_2\mathrm{\hspace{0.17em}}\to \mathrm{\hspace{0.17em}}{\mathrm{BrO}}_3^{-},$ the oxidation state of bromine changes from -

(1) – 1 to – 1

(2) 0 to – 1

(3) 0 to + 5

(4) 0 to – 5

Oxidation number of cobalt in K[Co(CO)₄] is

(1) + 1

(2) + 3

(3) – 1

(4) – 3

The oxidation number of nickel in Ni(CO)₄

1. 0

2. + 4

3. – 4

4. + 2