jee main chemistry important questions | d And f-Block Elements jee main questions FREE

Q 1 :
In alkaline medium, ${MnO}_{4}^{-}$ oxidises $I^{-}$ to [2024]

${IO}^{-}$
${IO}_{4}^{-}$
$I_{2}$
${IO}_{3}^{-}$

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(D)

In neutral or faintly alkaline medium, permanganate $({MnO}_{4}^{-})$ oxidizes iodide $(I^{-})$ to iodate $({IO}_{3}^{-})$

$2 {MnO}_{4}^{-} + H_{2} O + I^{-} \to 2 {MnO}_{2} + 2 {OH}^{-} + {IO}_{3}^{-}$

Q 2 :
${KMnO}_{4}$ decomposes on heating at 513K to form $O_{2}$ along with [2024]

${Mn and KO}_{2}$
$K_{2} {MnO}_{4} {and MnO}_{2}$
$K_{2} {MnO}_{4} and Mn$
${MnO}_{2} {and K}_{2} O_{2}$

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(B)

$2 {KMnO}_{4} (s) \overset{Δ}{\to} {MnO}_{2} (s) + K_{2} {MnO}_{4} (s) + O_{2} (g)$

Q 3 :
The orange colour of $K_{2} {Cr}_{2} O_{7}$ and purple colour of ${KMnO}_{4}$ is due to [2024]

Charge transfer transition in both.
d → d transitions in ${KMnO}_{4}$ and charge transfer transitions in $K_{2} {Cr}_{2} O_{7}$ .
d → d transitions in $K_{2} {Cr}_{2} O_{7}$ and charge transfer transitions in ${KMnO}_{4}$ .
d → d transitions in both

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(A)

A compound is coloured if it has electronic energy levels where electrons can undergo transition by absorbing light in visible range. For most d-block elements, energy difference in d-orbitals lies in visible range. Hence due to d-d electronic transitions, these are coloured. But in $K_{2} {Cr}_{2} O_{7}$ (orange) and ${KMnO}_{4}$ (purple), central atom has no d-electron. Colour of these compounds is due to charge transfer from oxide to metal ion.

Q 4 :
Alkaline oxidative fusion of ${MnO}_{2}$ gives ''A'' which on electrolytic oxidation in alkaline solution produces B. A and B respectively are [2024]

${Mn}_{2} O_{7}$ and ${MnO}_{4}^{-}$
${MnO}_{4}^{2 -}$ and ${MnO}_{4}^{-}$
${Mn}_{2} O_{3}$ and ${MnO}_{4}^{2 -}$
${MnO}_{4}^{2 -}$ and ${Mn}_{2} O_{7}$

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(B)

Alkaline oxidative fusion of ${MnO}_{2}$ gives manganate $({MnO}_{4}^{2 -})$ , which upon electrolytic oxidation gives permanganate.

$2 {MnO}_{2} + 4 KOH + O_{2} \to 2 K_{2} {MnO}_{4} + 2 H_{2} O$

${MnO}_{4}^{2 -} \overset{Electrolytic oxidation}{\to} {MnO}_{4}^{-}$

Manganate Permanganate

This is commercial method of preparation of Permanganate

Q 5 :
Identify correct statements from below:

A. The chromate ion is square planar.
B. Dichromates are generally prepared from chromates.
C. The green manganate ion is diamagnetic.
D. Dark green coloured $K_{2} {MnO}_{4}$ disproportionates in a neutral or acidic medium to give permanganate.
E. With increasing oxidation number of transition metal, ionic character of the oxides decreases.

Choose the correct answer from the options given below: [2024]

B, C, D only
A, D, E only
A, B, C only
B, D, E only

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(D)

(A) The chromate ion is tetrahedral in shape.

(B) Dichromates are prepared from chromates.

(C) In manganate ion, Mn is in +6 oxidation state, hence has one unpaired electron and is paramagnetic.

(D) The dark green $K_{2} {MnO}_{4}$ disproportionates in a neutral or acidic solution to give permanganate.

$2 {MnO}_{2} + 4 KOH + O_{2} \to 2 K_{2} {MnO}_{4} + 2 H_{2} O$

$3 {MnO}_{4}^{2 -} + 4 H^{+} \to 2 {MnO}_{4}^{-} + {MnO}_{2} + 2 H_{2} O$

(E) With increase in oxidation number of central metal atom, its polarising power increases and covalent character increase and therefore, ionic character decreases.

Q 6 :
Choose the correct statements from the following

A. ${Mn}_{2} O_{7}$ is an oil at room temperature
B. $V_{2} O_{4}$ reacts with acid to give ${VO}_{2}^{2 +}$
C. $CrO$ is a basic oxide
D. $V_{2} O_{5}$ does not react with acid

Choose the correct answer from the options given below: [2024]

A, B and D only
A and C only
A, B and C only
B and C only

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(B)

(A) ${Mn}_{2} O_{7}$ is a covalent green oil.

(B) $V_{2} O_{4}$ is a basic oxide. It dissolves in acids to give ${VO}^{2 +}$ salts (not ${VO}_{2}^{2 +}$ ).

(C) $CrO$ is basic and ${Cr}_{2} O_{3}$ is amphoteric.

(D) $V_{2} O_{5}$ is amphoteric. It reacts with alkalies as well as acids to give ${VO}_{4}^{3 -}$ respectively.

Q 7 :
Which of the following compounds show colour due to $d - d$ transition? [2024]

$K_{2} {Cr}_{2} O_{7}$
${CuSO}_{4} . 5 H_{2} O$
${KMnO}_{4}$
$K_{2} {CrO}_{4}$

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(B)

A compound is coloured if it has electronic energy levels where electrons can undergo transition by absorbing light in visible range. For most d block elements energy difference in d orbitals lies in visible range. Hence, due to d-d electronic transitions, These are coloured. In ${CuSO}_{4} . 5 H_{2} {O, Cu}^{2 +} (3 d^{9})$ splits into $t_{2 g}^{6}, e_{g}^{3}$ . $d - d$ transition from $t_{2 g}$ to $e_{g}$ makes it coloured. But in $K_{2} {Cr}_{2} O_{7}$ (orange), ${KMnO}_{4}$ (purple) and $K_{2} {CrO}_{4}$ (yellow), central atom has no d electron. Colour of these compounds is due to charge transfer from oxide to metal ion.

Q 8 :
Iron (III) catalyses the reaction between iodide and persulphate ions, in which

A. ${Fe}^{3 +}$ oxidises the iodide ion
B. ${Fe}^{3 +}$ oxidises the persulphate ion
C. ${Fe}^{2 +}$ reduces the iodide ion
D. ${Fe}^{2 +}$ reduces the persulphate ion

Choose the most appropriate answer from the options given below: [2024]

B only
A only
B and C only
A and D only

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(D)

$2 I^{-} + S_{2} O_{8}^{2 -} \to I_{2} + 2 {SO}_{4}^{2 -}$

In this reaction iron acts as catalyst as explained below:

${Fe}^{3 +}$ oxidizes the iodide ion

$2 {Fe}^{3 +} + 2 I^{-} \to 2 {Fe}^{2 +} + I_{2}$

${Fe}^{2 +}$ reduces the persulphate ion (oxygen is reduced from -1 to -2).

$2 {Fe}^{2 +} + S_{2} O_{8}^{2 -} \to 2 {Fe}^{3 +} + 2 {SO}_{4}^{2 -}$

Q 9 :
Given below are two statements:

Statement (I): Fusion of ${MnO}_{2}$ with KOH and an oxidising agent gives dark green $K_{2} {MnO}_{4}$ .

Statement (II): Manganate ion on electrolytic oxidation in alkaline medium gives permanganate ion.

In the light of the above statements, choose the correct answer from the options given below. [2024]

Statement I is true but Statement II is false
Both Statement I and Statement II are false
Statement I is false but Statement II is true
Both Statement I and Statement II are true

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(D)

Potassium permanganate is prepared by fusion of ${MnO}_{2}$ with an alkali metal hydroxide and an oxidising agent. This produces the dark green $K_{2} {MnO}_{4}$ which disproportionates in a neutral or acidic solution to give permanganate.

$2 {MnO}_{2} + 4 KOH + O_{2} \to 2 K_{2} {MnO}_{4} + 2 H_{2} O$

$3 {MnO}_{4}^{2 -} + 4 H^{+} \to 2 {MnO}_{4}^{-} + {MnO}_{2} + 2 H_{2} O$

Q 10 :
Number of moles of $H^{+}$ ions required by 1 mole of ${MnO}_{4}^{-}$ to oxidise oxalate ion to ${CO}_{2}$ is _____________ . [2024]

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(8)

${MnO}_{4}^{-}$ $+$ $8 H^{+}$ $+$ $5 e^{-}$ $\to$ ${Mn}^{2 +}$ $+$ $4 H_{2} O]$ $\times$ $2$

${C_{2} O}_{4}^{2 -}$ $\to$ $2 {CO}_{2}$ $+$ $2 e^{-}$ $]$ $\times$ $5$

_____________________________________________

$2 {MnO}_{4}^{-}$ $+$ $5 C_{2} O_{4}^{2 -}$ $+$ $16 H^{+}$ $\to$ $2 {Mn}^{2 +}$ $+$ $10 {CO}_{2}$ $+$ $8 H_{2} O$

Topic Question Set

Q 1 :
In alkaline medium, ${MnO}_{4}^{-}$ oxidises $I^{-}$ to [2024]

Q 2 :
${KMnO}_{4}$ decomposes on heating at 513K to form $O_{2}$ along with [2024]

Q 3 :
The orange colour of $K_{2} {Cr}_{2} O_{7}$ and purple colour of ${KMnO}_{4}$ is due to [2024]

Q 4 :
Alkaline oxidative fusion of ${MnO}_{2}$ gives ''A'' which on electrolytic oxidation in alkaline solution produces B. A and B respectively are [2024]

Q 6 :
Choose the correct statements from the following

A. ${Mn}_{2} O_{7}$ is an oil at room temperature
B. $V_{2} O_{4}$ reacts with acid to give ${VO}_{2}^{2 +}$
C. $CrO$ is a basic oxide
D. $V_{2} O_{5}$ does not react with acid

Choose the correct answer from the options given below: [2024]

Q 7 :
Which of the following compounds show colour due to $d - d$ transition? [2024]

Q 10 :
Number of moles of $H^{+}$ ions required by 1 mole of ${MnO}_{4}^{-}$ to oxidise oxalate ion to ${CO}_{2}$ is _____________ . [2024]

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Topic Question Set

Q 1 : In alkaline medium, MnO4- oxidises I- to [2024]

Q 2 : KMnO4 decomposes on heating at 513K to form O2 along with [2024]

Q 3 : The orange colour of K2Cr2O7 and purple colour of KMnO4 is due to [2024]

Q 4 : Alkaline oxidative fusion of MnO2 gives ''A'' which on electrolytic oxidation in alkaline solution produces B. A and B respectively are [2024]

Q 6 : Choose the correct statements from the following A. Mn2O7 is an oil at room temperature B. V2O4 reacts with acid to give VO22+ C. CrO is a basic oxide D. V2O5 does not react with acid Choose the correct answer from the options given below: [2024]

Q 7 : Which of the following compounds show colour due to d-d transition? [2024]

Q 8 : Iron (III) catalyses the reaction between iodide and persulphate ions, in which A. Fe3+ oxidises the iodide ion B. Fe3+ oxidises the persulphate ion C. Fe2+ reduces the iodide ion D. Fe2+ reduces the persulphate ion Choose the most appropriate answer from the options given below: [2024]

Q 10 : Number of moles of H+ ions required by 1 mole of MnO4- to oxidise oxalate ion to CO2 is _____________ . [2024]

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Q 1 :
In alkaline medium, ${MnO}_{4}^{-}$ oxidises $I^{-}$ to [2024]

Q 2 :
${KMnO}_{4}$ decomposes on heating at 513K to form $O_{2}$ along with [2024]

Q 3 :
The orange colour of $K_{2} {Cr}_{2} O_{7}$ and purple colour of ${KMnO}_{4}$ is due to [2024]

Q 4 :
Alkaline oxidative fusion of ${MnO}_{2}$ gives ''A'' which on electrolytic oxidation in alkaline solution produces B. A and B respectively are [2024]

Q 6 :
Choose the correct statements from the following

A. ${Mn}_{2} O_{7}$ is an oil at room temperature
B. $V_{2} O_{4}$ reacts with acid to give ${VO}_{2}^{2 +}$
C. $CrO$ is a basic oxide
D. $V_{2} O_{5}$ does not react with acid

Choose the correct answer from the options given below: [2024]

Q 7 :
Which of the following compounds show colour due to $d - d$ transition? [2024]

Q 10 :
Number of moles of $H^{+}$ ions required by 1 mole of ${MnO}_{4}^{-}$ to oxidise oxalate ion to ${CO}_{2}$ is _____________ . [2024]