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CHXII08:THE D- & F-BLOCK ELEMENTS

321284 In the dichromate dianion,

1

4 C r - O

bonds are equivalent

2

6 C r - O

bonds are equivalent

3 all

Cr - O

bonds are equivalent

4 all

Cr - O

bonds are nonequivalent

Explanation:

The structure of $C r_{2} O_{7}^{2 -}$
supporting img
There are six normal Cr - O bonds and two bridged Cr - O bond.
The six normal Cr - O bonds are expected to be equivalent and different from those of the bridged Cr - O bond.

CHXII08:THE D- & F-BLOCK ELEMENTS

321285 $(X) + K_{2} {CO}_{3} + Air \overset{Heat}{⟶} (Y)$ .
$(Y) + {Cl}_{2} ⟶ (Z)$ Pink
Which of the following is correct?

1

X =

Black,

{MnO}_{2}, Y =

Blue,

K_{2} {CrO}_{4}, Z = {KMnO}_{4} .

2

X =

Green,

{Cr}_{2} O_{3}, Y =

Yellow,

K_{2} {CrO}_{4}, Z = K_{2} {Cr}_{2} O_{7}

.

3

X =

Black,

{MnO}_{2}, Y =

Green,

K_{2} {MnO}_{4}, Z = {KMnO}_{4}

.

4

X =

Black,

{Bi}_{2} O_{3}, Y =

Colourless,

{KBiO}_{2}, Z = {KBiO}_{3}

.

Explanation:

$Mn O_{2} + K_{2} C O_{3} + Air \overset{Heat}{\to} K_{2} Mn O_{4}$
$(X) (Y)$
$K_{2} M n O_{4} + C l_{2} \to K M n O_{4} + K C l$
$(Z)$

CHXII08:THE D- & F-BLOCK ELEMENTS

321286 In acidic medium, $K_{2} {Cr}_{2} O_{7}$ shows oxidising action as represented in the half reaction
${Cr}_{2} O_{7}^{2 -} + {XH}^{+} + {Ye}^{-} \to 2 A + {ZH}_{2} O$
$X, Y, Z$ and A respectively are

1

8, 4, 6

and

{Cr}_{2} O_{3}

2

14, 7, 6

and

{Cr}^{3 +}

3

14, 6, 7

and

{Cr}^{3 +}

4

8, 6, 4

and

{Cr}_{2} O_{3}

Explanation:

The balanced half reaction will be
${Cr}_{2} O_{7}^{2 -} + 14 H^{+} + 6 e^{-} \to 2 {Cr}^{3 +} + 7 H_{2} O$
So, $X = 14, Y = 6, Z = 7, A = {Cr}^{3 +}$
So, the correct option is (3).

JEE Main - 2024

CHXII08:THE D- & F-BLOCK ELEMENTS

321287 Which of the following statements is false?

1 An acidified solution of

K_{2} {Cr}_{2} O_{7}

liberates iodine from potassium iodide.

2 In acidic solution, dichromate ions are converted to chromate ions.

3 Ammonium dichromate on heating under goes endothermic decomposition to give

{Cr}_{2} O_{3}

.

4 Potassium dichromate is used as a titrant for

{Fe}^{2 +}

ions.

CHXII08:THE D- & F-BLOCK ELEMENTS

321284 In the dichromate dianion,

1

4 C r - O

bonds are equivalent

2

6 C r - O

bonds are equivalent

3 all

Cr - O

bonds are equivalent

4 all

Cr - O

bonds are nonequivalent

Explanation:

The structure of $C r_{2} O_{7}^{2 -}$
supporting img
There are six normal Cr - O bonds and two bridged Cr - O bond.
The six normal Cr - O bonds are expected to be equivalent and different from those of the bridged Cr - O bond.

CHXII08:THE D- & F-BLOCK ELEMENTS

321285 $(X) + K_{2} {CO}_{3} + Air \overset{Heat}{⟶} (Y)$ .
$(Y) + {Cl}_{2} ⟶ (Z)$ Pink
Which of the following is correct?

1

X =

Black,

{MnO}_{2}, Y =

Blue,

K_{2} {CrO}_{4}, Z = {KMnO}_{4} .

2

X =

Green,

{Cr}_{2} O_{3}, Y =

Yellow,

K_{2} {CrO}_{4}, Z = K_{2} {Cr}_{2} O_{7}

.

3

X =

Black,

{MnO}_{2}, Y =

Green,

K_{2} {MnO}_{4}, Z = {KMnO}_{4}

.

4

X =

Black,

{Bi}_{2} O_{3}, Y =

Colourless,

{KBiO}_{2}, Z = {KBiO}_{3}

.

Explanation:

$Mn O_{2} + K_{2} C O_{3} + Air \overset{Heat}{\to} K_{2} Mn O_{4}$
$(X) (Y)$
$K_{2} M n O_{4} + C l_{2} \to K M n O_{4} + K C l$
$(Z)$

CHXII08:THE D- & F-BLOCK ELEMENTS

321286 In acidic medium, $K_{2} {Cr}_{2} O_{7}$ shows oxidising action as represented in the half reaction
${Cr}_{2} O_{7}^{2 -} + {XH}^{+} + {Ye}^{-} \to 2 A + {ZH}_{2} O$
$X, Y, Z$ and A respectively are

1

8, 4, 6

and

{Cr}_{2} O_{3}

2

14, 7, 6

and

{Cr}^{3 +}

3

14, 6, 7

and

{Cr}^{3 +}

4

8, 6, 4

and

{Cr}_{2} O_{3}

Explanation:

The balanced half reaction will be
${Cr}_{2} O_{7}^{2 -} + 14 H^{+} + 6 e^{-} \to 2 {Cr}^{3 +} + 7 H_{2} O$
So, $X = 14, Y = 6, Z = 7, A = {Cr}^{3 +}$
So, the correct option is (3).

JEE Main - 2024

CHXII08:THE D- & F-BLOCK ELEMENTS

321287 Which of the following statements is false?

1 An acidified solution of

K_{2} {Cr}_{2} O_{7}

liberates iodine from potassium iodide.

2 In acidic solution, dichromate ions are converted to chromate ions.

3 Ammonium dichromate on heating under goes endothermic decomposition to give

{Cr}_{2} O_{3}

.

4 Potassium dichromate is used as a titrant for

{Fe}^{2 +}

ions.

CHXII08:THE D- & F-BLOCK ELEMENTS

321284 In the dichromate dianion,

1

4 C r - O

bonds are equivalent

2

6 C r - O

bonds are equivalent

3 all

Cr - O

bonds are equivalent

4 all

Cr - O

bonds are nonequivalent

Explanation:

The structure of $C r_{2} O_{7}^{2 -}$
supporting img
There are six normal Cr - O bonds and two bridged Cr - O bond.
The six normal Cr - O bonds are expected to be equivalent and different from those of the bridged Cr - O bond.

CHXII08:THE D- & F-BLOCK ELEMENTS

321285 $(X) + K_{2} {CO}_{3} + Air \overset{Heat}{⟶} (Y)$ .
$(Y) + {Cl}_{2} ⟶ (Z)$ Pink
Which of the following is correct?

1

X =

Black,

{MnO}_{2}, Y =

Blue,

K_{2} {CrO}_{4}, Z = {KMnO}_{4} .

2

X =

Green,

{Cr}_{2} O_{3}, Y =

Yellow,

K_{2} {CrO}_{4}, Z = K_{2} {Cr}_{2} O_{7}

.

3

X =

Black,

{MnO}_{2}, Y =

Green,

K_{2} {MnO}_{4}, Z = {KMnO}_{4}

.

4

X =

Black,

{Bi}_{2} O_{3}, Y =

Colourless,

{KBiO}_{2}, Z = {KBiO}_{3}

.

Explanation:

$Mn O_{2} + K_{2} C O_{3} + Air \overset{Heat}{\to} K_{2} Mn O_{4}$
$(X) (Y)$
$K_{2} M n O_{4} + C l_{2} \to K M n O_{4} + K C l$
$(Z)$

CHXII08:THE D- & F-BLOCK ELEMENTS

321286 In acidic medium, $K_{2} {Cr}_{2} O_{7}$ shows oxidising action as represented in the half reaction
${Cr}_{2} O_{7}^{2 -} + {XH}^{+} + {Ye}^{-} \to 2 A + {ZH}_{2} O$
$X, Y, Z$ and A respectively are

1

8, 4, 6

and

{Cr}_{2} O_{3}

2

14, 7, 6

and

{Cr}^{3 +}

3

14, 6, 7

and

{Cr}^{3 +}

4

8, 6, 4

and

{Cr}_{2} O_{3}

Explanation:

The balanced half reaction will be
${Cr}_{2} O_{7}^{2 -} + 14 H^{+} + 6 e^{-} \to 2 {Cr}^{3 +} + 7 H_{2} O$
So, $X = 14, Y = 6, Z = 7, A = {Cr}^{3 +}$
So, the correct option is (3).

JEE Main - 2024

CHXII08:THE D- & F-BLOCK ELEMENTS

321287 Which of the following statements is false?

1 An acidified solution of

K_{2} {Cr}_{2} O_{7}

liberates iodine from potassium iodide.

2 In acidic solution, dichromate ions are converted to chromate ions.

3 Ammonium dichromate on heating under goes endothermic decomposition to give

{Cr}_{2} O_{3}

.

4 Potassium dichromate is used as a titrant for

{Fe}^{2 +}

ions.

CHXII08:THE D- & F-BLOCK ELEMENTS

321284 In the dichromate dianion,

1

4 C r - O

bonds are equivalent

2

6 C r - O

bonds are equivalent

3 all

Cr - O

bonds are equivalent

4 all

Cr - O

bonds are nonequivalent

Explanation:

The structure of $C r_{2} O_{7}^{2 -}$
supporting img
There are six normal Cr - O bonds and two bridged Cr - O bond.
The six normal Cr - O bonds are expected to be equivalent and different from those of the bridged Cr - O bond.

CHXII08:THE D- & F-BLOCK ELEMENTS

321285 $(X) + K_{2} {CO}_{3} + Air \overset{Heat}{⟶} (Y)$ .
$(Y) + {Cl}_{2} ⟶ (Z)$ Pink
Which of the following is correct?

1

X =

Black,

{MnO}_{2}, Y =

Blue,

K_{2} {CrO}_{4}, Z = {KMnO}_{4} .

2

X =

Green,

{Cr}_{2} O_{3}, Y =

Yellow,

K_{2} {CrO}_{4}, Z = K_{2} {Cr}_{2} O_{7}

.

3

X =

Black,

{MnO}_{2}, Y =

Green,

K_{2} {MnO}_{4}, Z = {KMnO}_{4}

.

4

X =

Black,

{Bi}_{2} O_{3}, Y =

Colourless,

{KBiO}_{2}, Z = {KBiO}_{3}

.

Explanation:

$Mn O_{2} + K_{2} C O_{3} + Air \overset{Heat}{\to} K_{2} Mn O_{4}$
$(X) (Y)$
$K_{2} M n O_{4} + C l_{2} \to K M n O_{4} + K C l$
$(Z)$

CHXII08:THE D- & F-BLOCK ELEMENTS

321286 In acidic medium, $K_{2} {Cr}_{2} O_{7}$ shows oxidising action as represented in the half reaction
${Cr}_{2} O_{7}^{2 -} + {XH}^{+} + {Ye}^{-} \to 2 A + {ZH}_{2} O$
$X, Y, Z$ and A respectively are

1

8, 4, 6

and

{Cr}_{2} O_{3}

2

14, 7, 6

and

{Cr}^{3 +}

3

14, 6, 7

and

{Cr}^{3 +}

4

8, 6, 4

and

{Cr}_{2} O_{3}

Explanation:

The balanced half reaction will be
${Cr}_{2} O_{7}^{2 -} + 14 H^{+} + 6 e^{-} \to 2 {Cr}^{3 +} + 7 H_{2} O$
So, $X = 14, Y = 6, Z = 7, A = {Cr}^{3 +}$
So, the correct option is (3).

JEE Main - 2024

CHXII08:THE D- & F-BLOCK ELEMENTS

321287 Which of the following statements is false?

1 An acidified solution of

K_{2} {Cr}_{2} O_{7}

liberates iodine from potassium iodide.

2 In acidic solution, dichromate ions are converted to chromate ions.

3 Ammonium dichromate on heating under goes endothermic decomposition to give

{Cr}_{2} O_{3}

.

4 Potassium dichromate is used as a titrant for

{Fe}^{2 +}

ions.

Explanation:

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