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CHXII08:THE D- & F-BLOCK ELEMENTS

321262 Which of the following is correct?

1

{CrO}_{3}

has peroxide bond in its structure.

2 Heating

{({NH}_{4})}_{2} {Cr}_{2} O_{7}

produces

{Cr}_{2} O_{3}

along with

O_{2}

.

3 Acidification of

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

turns it yellow.

4

{Cl}_{2}

is liberated in little amount when

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

and conc.

H_{2} {SO}_{4}

are heated together.

Explanation:

$\begin{aligned} K_{2} {Cr}_{2} O_{7} + 6 KCl + & 7 H_{2} {SO}_{4} \to {Cr}_{2} {({SO}_{4})}_{3} \\ + 4 K_{2} {SO}_{4} + 3 {Cl}_{2} + 7 H_{2} O \end{aligned}$

CHXII08:THE D- & F-BLOCK ELEMENTS

321263 The yellow colour of chromates changes to orange on acidification due to the formation of:

1

{Cr}^{3 +}

2

{Cr}_{2} O_{3}

3

{Cr}_{2} O_{7}^{2 -}

4

{CrO}_{4}^{- 2}

Explanation:

${CrO}_{4}^{2 -}$ (yellow) $\overset{H^{+}}{⟶} {Cr}_{2} O_{7}^{2 -}$ (orange)

CHXII08:THE D- & F-BLOCK ELEMENTS

321264 The oxidation number is changed in which of the following case

1

{SO}_{2}

gas is passed into

{Cr}_{2} O_{7}^{2 -} / H^{+}

2 Aqueous solution of

{Cr}_{2} O_{4}^{2 -}

is acidified

3

{CrO}_{2} {Cl}_{2}

is dissolved in

NaOH

4

{Cr}_{2} O_{7}^{2 -}

solution is made alkaline

Explanation:

(1) $\overset{+ 6}{C r_{2} O_{7}^{2 -}} + \overset{+ 4}{S O_{2}} + 2 H^{+} \to \overset{+ 3}{2 C r^{3 +}} + \overset{+ 6}{{3 S O}_{4}^{2 -}} + H_{2} O$
(2) $\overset{+ 6}{{2 C r O}_{4}^{2 -}} + 2 H^{+} \to \overset{+ 6}{C r_{2} O_{7}^{2 -}} + H_{2} O$
(3) $\overset{+ 6}{C r O_{2} C l_{2}} + 2 N a O H \to \overset{+ 6}{N a_{2} C r O_{4}}$
(4) $\overset{+ 6}{C r_{2} O_{7}^{2 -}} + 2 O H^{-} \to \overset{+ 6}{{2 C r O}_{4}^{2 -}} + H_{2} O$

CHXII08:THE D- & F-BLOCK ELEMENTS

321265 The number of $Cr - O$ bonds in dichromate ion is

1 6

2 7

3 8

4 4

Explanation:

$8 Cr - O$ bonds present in dichromate ion.

NCERT Exemplar

CHXII08:THE D- & F-BLOCK ELEMENTS

321266 Assertion :
$K_{2} {Cr}_{2} O_{7}$ is used as primary standard in volumetric analysis.
Reason :
It has a good solubility in water.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but Reason is correct.

Explanation:

$K_{2} {Cr}_{2} O_{7}$ is less soluble in water .
$K_{2} {Cr}_{2} O_{7}$ can be found in pure state and can be accurately weighed. It is not hygroscopic in nature. So, $K_{2} {Cr}_{2} O_{7}$ is used as a primary standard solution. Thus, option (3) is correct.

CHXII08:THE D- & F-BLOCK ELEMENTS

321262 Which of the following is correct?

1

{CrO}_{3}

has peroxide bond in its structure.

2 Heating

{({NH}_{4})}_{2} {Cr}_{2} O_{7}

produces

{Cr}_{2} O_{3}

along with

O_{2}

.

3 Acidification of

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

turns it yellow.

4

{Cl}_{2}

is liberated in little amount when

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

and conc.

H_{2} {SO}_{4}

are heated together.

Explanation:

$\begin{aligned} K_{2} {Cr}_{2} O_{7} + 6 KCl + & 7 H_{2} {SO}_{4} \to {Cr}_{2} {({SO}_{4})}_{3} \\ + 4 K_{2} {SO}_{4} + 3 {Cl}_{2} + 7 H_{2} O \end{aligned}$

CHXII08:THE D- & F-BLOCK ELEMENTS

321263 The yellow colour of chromates changes to orange on acidification due to the formation of:

1

{Cr}^{3 +}

2

{Cr}_{2} O_{3}

3

{Cr}_{2} O_{7}^{2 -}

4

{CrO}_{4}^{- 2}

Explanation:

${CrO}_{4}^{2 -}$ (yellow) $\overset{H^{+}}{⟶} {Cr}_{2} O_{7}^{2 -}$ (orange)

CHXII08:THE D- & F-BLOCK ELEMENTS

321264 The oxidation number is changed in which of the following case

1

{SO}_{2}

gas is passed into

{Cr}_{2} O_{7}^{2 -} / H^{+}

2 Aqueous solution of

{Cr}_{2} O_{4}^{2 -}

is acidified

3

{CrO}_{2} {Cl}_{2}

is dissolved in

NaOH

4

{Cr}_{2} O_{7}^{2 -}

solution is made alkaline

Explanation:

(1) $\overset{+ 6}{C r_{2} O_{7}^{2 -}} + \overset{+ 4}{S O_{2}} + 2 H^{+} \to \overset{+ 3}{2 C r^{3 +}} + \overset{+ 6}{{3 S O}_{4}^{2 -}} + H_{2} O$
(2) $\overset{+ 6}{{2 C r O}_{4}^{2 -}} + 2 H^{+} \to \overset{+ 6}{C r_{2} O_{7}^{2 -}} + H_{2} O$
(3) $\overset{+ 6}{C r O_{2} C l_{2}} + 2 N a O H \to \overset{+ 6}{N a_{2} C r O_{4}}$
(4) $\overset{+ 6}{C r_{2} O_{7}^{2 -}} + 2 O H^{-} \to \overset{+ 6}{{2 C r O}_{4}^{2 -}} + H_{2} O$

CHXII08:THE D- & F-BLOCK ELEMENTS

321265 The number of $Cr - O$ bonds in dichromate ion is

1 6

2 7

3 8

4 4

Explanation:

$8 Cr - O$ bonds present in dichromate ion.

NCERT Exemplar

CHXII08:THE D- & F-BLOCK ELEMENTS

321266 Assertion :
$K_{2} {Cr}_{2} O_{7}$ is used as primary standard in volumetric analysis.
Reason :
It has a good solubility in water.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but Reason is correct.

Explanation:

$K_{2} {Cr}_{2} O_{7}$ is less soluble in water .
$K_{2} {Cr}_{2} O_{7}$ can be found in pure state and can be accurately weighed. It is not hygroscopic in nature. So, $K_{2} {Cr}_{2} O_{7}$ is used as a primary standard solution. Thus, option (3) is correct.

CHXII08:THE D- & F-BLOCK ELEMENTS

321262 Which of the following is correct?

1

{CrO}_{3}

has peroxide bond in its structure.

2 Heating

{({NH}_{4})}_{2} {Cr}_{2} O_{7}

produces

{Cr}_{2} O_{3}

along with

O_{2}

.

3 Acidification of

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

turns it yellow.

4

{Cl}_{2}

is liberated in little amount when

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

and conc.

H_{2} {SO}_{4}

are heated together.

Explanation:

$\begin{aligned} K_{2} {Cr}_{2} O_{7} + 6 KCl + & 7 H_{2} {SO}_{4} \to {Cr}_{2} {({SO}_{4})}_{3} \\ + 4 K_{2} {SO}_{4} + 3 {Cl}_{2} + 7 H_{2} O \end{aligned}$

CHXII08:THE D- & F-BLOCK ELEMENTS

321263 The yellow colour of chromates changes to orange on acidification due to the formation of:

1

{Cr}^{3 +}

2

{Cr}_{2} O_{3}

3

{Cr}_{2} O_{7}^{2 -}

4

{CrO}_{4}^{- 2}

Explanation:

${CrO}_{4}^{2 -}$ (yellow) $\overset{H^{+}}{⟶} {Cr}_{2} O_{7}^{2 -}$ (orange)

CHXII08:THE D- & F-BLOCK ELEMENTS

321264 The oxidation number is changed in which of the following case

1

{SO}_{2}

gas is passed into

{Cr}_{2} O_{7}^{2 -} / H^{+}

2 Aqueous solution of

{Cr}_{2} O_{4}^{2 -}

is acidified

3

{CrO}_{2} {Cl}_{2}

is dissolved in

NaOH

4

{Cr}_{2} O_{7}^{2 -}

solution is made alkaline

Explanation:

(1) $\overset{+ 6}{C r_{2} O_{7}^{2 -}} + \overset{+ 4}{S O_{2}} + 2 H^{+} \to \overset{+ 3}{2 C r^{3 +}} + \overset{+ 6}{{3 S O}_{4}^{2 -}} + H_{2} O$
(2) $\overset{+ 6}{{2 C r O}_{4}^{2 -}} + 2 H^{+} \to \overset{+ 6}{C r_{2} O_{7}^{2 -}} + H_{2} O$
(3) $\overset{+ 6}{C r O_{2} C l_{2}} + 2 N a O H \to \overset{+ 6}{N a_{2} C r O_{4}}$
(4) $\overset{+ 6}{C r_{2} O_{7}^{2 -}} + 2 O H^{-} \to \overset{+ 6}{{2 C r O}_{4}^{2 -}} + H_{2} O$

CHXII08:THE D- & F-BLOCK ELEMENTS

321265 The number of $Cr - O$ bonds in dichromate ion is

1 6

2 7

3 8

4 4

Explanation:

$8 Cr - O$ bonds present in dichromate ion.

NCERT Exemplar

CHXII08:THE D- & F-BLOCK ELEMENTS

321266 Assertion :
$K_{2} {Cr}_{2} O_{7}$ is used as primary standard in volumetric analysis.
Reason :
It has a good solubility in water.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but Reason is correct.

Explanation:

$K_{2} {Cr}_{2} O_{7}$ is less soluble in water .
$K_{2} {Cr}_{2} O_{7}$ can be found in pure state and can be accurately weighed. It is not hygroscopic in nature. So, $K_{2} {Cr}_{2} O_{7}$ is used as a primary standard solution. Thus, option (3) is correct.

CHXII08:THE D- & F-BLOCK ELEMENTS

321262 Which of the following is correct?

1

{CrO}_{3}

has peroxide bond in its structure.

2 Heating

{({NH}_{4})}_{2} {Cr}_{2} O_{7}

produces

{Cr}_{2} O_{3}

along with

O_{2}

.

3 Acidification of

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

turns it yellow.

4

{Cl}_{2}

is liberated in little amount when

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

and conc.

H_{2} {SO}_{4}

are heated together.

Explanation:

$\begin{aligned} K_{2} {Cr}_{2} O_{7} + 6 KCl + & 7 H_{2} {SO}_{4} \to {Cr}_{2} {({SO}_{4})}_{3} \\ + 4 K_{2} {SO}_{4} + 3 {Cl}_{2} + 7 H_{2} O \end{aligned}$

CHXII08:THE D- & F-BLOCK ELEMENTS

321263 The yellow colour of chromates changes to orange on acidification due to the formation of:

1

{Cr}^{3 +}

2

{Cr}_{2} O_{3}

3

{Cr}_{2} O_{7}^{2 -}

4

{CrO}_{4}^{- 2}

Explanation:

${CrO}_{4}^{2 -}$ (yellow) $\overset{H^{+}}{⟶} {Cr}_{2} O_{7}^{2 -}$ (orange)

CHXII08:THE D- & F-BLOCK ELEMENTS

321264 The oxidation number is changed in which of the following case

1

{SO}_{2}

gas is passed into

{Cr}_{2} O_{7}^{2 -} / H^{+}

2 Aqueous solution of

{Cr}_{2} O_{4}^{2 -}

is acidified

3

{CrO}_{2} {Cl}_{2}

is dissolved in

NaOH

4

{Cr}_{2} O_{7}^{2 -}

solution is made alkaline

Explanation:

(1) $\overset{+ 6}{C r_{2} O_{7}^{2 -}} + \overset{+ 4}{S O_{2}} + 2 H^{+} \to \overset{+ 3}{2 C r^{3 +}} + \overset{+ 6}{{3 S O}_{4}^{2 -}} + H_{2} O$
(2) $\overset{+ 6}{{2 C r O}_{4}^{2 -}} + 2 H^{+} \to \overset{+ 6}{C r_{2} O_{7}^{2 -}} + H_{2} O$
(3) $\overset{+ 6}{C r O_{2} C l_{2}} + 2 N a O H \to \overset{+ 6}{N a_{2} C r O_{4}}$
(4) $\overset{+ 6}{C r_{2} O_{7}^{2 -}} + 2 O H^{-} \to \overset{+ 6}{{2 C r O}_{4}^{2 -}} + H_{2} O$

CHXII08:THE D- & F-BLOCK ELEMENTS

321265 The number of $Cr - O$ bonds in dichromate ion is

1 6

2 7

3 8

4 4

Explanation:

$8 Cr - O$ bonds present in dichromate ion.

NCERT Exemplar

CHXII08:THE D- & F-BLOCK ELEMENTS

321266 Assertion :
$K_{2} {Cr}_{2} O_{7}$ is used as primary standard in volumetric analysis.
Reason :
It has a good solubility in water.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but Reason is correct.

Explanation:

$K_{2} {Cr}_{2} O_{7}$ is less soluble in water .
$K_{2} {Cr}_{2} O_{7}$ can be found in pure state and can be accurately weighed. It is not hygroscopic in nature. So, $K_{2} {Cr}_{2} O_{7}$ is used as a primary standard solution. Thus, option (3) is correct.

CHXII08:THE D- & F-BLOCK ELEMENTS

321262 Which of the following is correct?

1

{CrO}_{3}

has peroxide bond in its structure.

2 Heating

{({NH}_{4})}_{2} {Cr}_{2} O_{7}

produces

{Cr}_{2} O_{3}

along with

O_{2}

.

3 Acidification of

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

turns it yellow.

4

{Cl}_{2}

is liberated in little amount when

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

and conc.

H_{2} {SO}_{4}

are heated together.

Explanation:

$\begin{aligned} K_{2} {Cr}_{2} O_{7} + 6 KCl + & 7 H_{2} {SO}_{4} \to {Cr}_{2} {({SO}_{4})}_{3} \\ + 4 K_{2} {SO}_{4} + 3 {Cl}_{2} + 7 H_{2} O \end{aligned}$

CHXII08:THE D- & F-BLOCK ELEMENTS

321263 The yellow colour of chromates changes to orange on acidification due to the formation of:

1

{Cr}^{3 +}

2

{Cr}_{2} O_{3}

3

{Cr}_{2} O_{7}^{2 -}

4

{CrO}_{4}^{- 2}

Explanation:

${CrO}_{4}^{2 -}$ (yellow) $\overset{H^{+}}{⟶} {Cr}_{2} O_{7}^{2 -}$ (orange)

CHXII08:THE D- & F-BLOCK ELEMENTS

321264 The oxidation number is changed in which of the following case

1

{SO}_{2}

gas is passed into

{Cr}_{2} O_{7}^{2 -} / H^{+}

2 Aqueous solution of

{Cr}_{2} O_{4}^{2 -}

is acidified

3

{CrO}_{2} {Cl}_{2}

is dissolved in

NaOH

4

{Cr}_{2} O_{7}^{2 -}

solution is made alkaline

Explanation:

(1) $\overset{+ 6}{C r_{2} O_{7}^{2 -}} + \overset{+ 4}{S O_{2}} + 2 H^{+} \to \overset{+ 3}{2 C r^{3 +}} + \overset{+ 6}{{3 S O}_{4}^{2 -}} + H_{2} O$
(2) $\overset{+ 6}{{2 C r O}_{4}^{2 -}} + 2 H^{+} \to \overset{+ 6}{C r_{2} O_{7}^{2 -}} + H_{2} O$
(3) $\overset{+ 6}{C r O_{2} C l_{2}} + 2 N a O H \to \overset{+ 6}{N a_{2} C r O_{4}}$
(4) $\overset{+ 6}{C r_{2} O_{7}^{2 -}} + 2 O H^{-} \to \overset{+ 6}{{2 C r O}_{4}^{2 -}} + H_{2} O$

CHXII08:THE D- & F-BLOCK ELEMENTS

321265 The number of $Cr - O$ bonds in dichromate ion is

1 6

2 7

3 8

4 4

Explanation:

$8 Cr - O$ bonds present in dichromate ion.

NCERT Exemplar

CHXII08:THE D- & F-BLOCK ELEMENTS

321266 Assertion :
$K_{2} {Cr}_{2} O_{7}$ is used as primary standard in volumetric analysis.
Reason :
It has a good solubility in water.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but Reason is correct.

Explanation:

$K_{2} {Cr}_{2} O_{7}$ is less soluble in water .
$K_{2} {Cr}_{2} O_{7}$ can be found in pure state and can be accurately weighed. It is not hygroscopic in nature. So, $K_{2} {Cr}_{2} O_{7}$ is used as a primary standard solution. Thus, option (3) is correct.

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