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CHXII08:THE D- & F-BLOCK ELEMENTS

321279 ${CrO}_{3}$ dissolves in aq. NaOH to give

1

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

2

Cr (OH)_{2}

3

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

4

Cr (OH)_{3}

Explanation:

${CrO}_{3} + 2 {OH}^{-} \to {CrO}_{4}^{- 2} + H_{2} O$

CHXII08:THE D- & F-BLOCK ELEMENTS

321280 Assertion :
Solution of ${Na}_{2} {CrO}_{4}$ in water is intensely coloured.
Reason :
Oxidation state of $Cr$ in ${Na}_{2} {CrO}_{4}$ is $(+ VI)$ .

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 Both Assertion and Reason is incorrect.

Explanation:

In $N a_{2} Cr O_{4},$ is in +6 oxidation state with $d^{\circ}$ configuration. The ${CrO}_{4}^{2 -}$ ions in aqueous solution give yellow colour which is not due to $d - d$ transition but due to charge transfer, i.e., momentary transfer of charge from oxygen atom to metal atom.
Hence, both Assertion and Reason are correct but Reason is not the correct explanation of Assertion.

AIIMS - 2013

CHXII08:THE D- & F-BLOCK ELEMENTS

321281 Potassium dichromate acts as a strong oxidising agent in acidic solution. During this process, the oxidation state changes from

1

+ 6

to

+ 3

2

+ 3

to

+ 1

3

+ 6

to

+ 2

4

+ 2

to

+ 1

Explanation:

In acidic medium,
$\overset{+ 6}{{Cr}_{2}} O_{7}^{2 -} + 14 H^{+} + 6 e^{-} \to 2 {Cr}^{+ 3} + 7 H_{2} O$
The oxidation state changes from $+ 6$ to $+ 3$ .

JEE - 2023

CHXII08:THE D- & F-BLOCK ELEMENTS

321282 Assertion :
Solution of ${Na}_{2} {CrO}_{4}$ in water is intensely coloured.
Reason :
Oxidation state of $Cr$ in ${Na}_{2} {CrO}_{4}$ is $+ VI$ .

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:

${Na}_{2} {CrO}_{4}$ solution in water is yellow in colour, when acidified it changes to orange colour (due to the formation of ${Cr}_{2} O_{7}^{2 -}$ ions).
$2 {Na}_{2} {Cr}_{2} O_{4} + H_{2} {SO}_{4} \to$
${Na}_{2} {Cr}_{2} O_{7} + {Na}_{2} {SO}_{4} + H_{2} O$
Let oxidation state of $Cr$ in ${Na}_{2} {Cr}_{2} O_{4}$ be x.
$\Rightarrow 2 (+ 1) + x + 4 (- 2) = 0 \Rightarrow x = + 6$ .
So option (2) is correct.

CHXII08:THE D- & F-BLOCK ELEMENTS

321283 The number of $Cr - O - Cr$ bonds in dichromate ion is ____ .

1 1

2 0

3 2

4 3

CHXII08:THE D- & F-BLOCK ELEMENTS

321279 ${CrO}_{3}$ dissolves in aq. NaOH to give

1

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

2

Cr (OH)_{2}

3

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

4

Cr (OH)_{3}

Explanation:

${CrO}_{3} + 2 {OH}^{-} \to {CrO}_{4}^{- 2} + H_{2} O$

CHXII08:THE D- & F-BLOCK ELEMENTS

321280 Assertion :
Solution of ${Na}_{2} {CrO}_{4}$ in water is intensely coloured.
Reason :
Oxidation state of $Cr$ in ${Na}_{2} {CrO}_{4}$ is $(+ VI)$ .

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 Both Assertion and Reason is incorrect.

Explanation:

In $N a_{2} Cr O_{4},$ is in +6 oxidation state with $d^{\circ}$ configuration. The ${CrO}_{4}^{2 -}$ ions in aqueous solution give yellow colour which is not due to $d - d$ transition but due to charge transfer, i.e., momentary transfer of charge from oxygen atom to metal atom.
Hence, both Assertion and Reason are correct but Reason is not the correct explanation of Assertion.

AIIMS - 2013

CHXII08:THE D- & F-BLOCK ELEMENTS

321281 Potassium dichromate acts as a strong oxidising agent in acidic solution. During this process, the oxidation state changes from

1

+ 6

to

+ 3

2

+ 3

to

+ 1

3

+ 6

to

+ 2

4

+ 2

to

+ 1

Explanation:

In acidic medium,
$\overset{+ 6}{{Cr}_{2}} O_{7}^{2 -} + 14 H^{+} + 6 e^{-} \to 2 {Cr}^{+ 3} + 7 H_{2} O$
The oxidation state changes from $+ 6$ to $+ 3$ .

JEE - 2023

CHXII08:THE D- & F-BLOCK ELEMENTS

321282 Assertion :
Solution of ${Na}_{2} {CrO}_{4}$ in water is intensely coloured.
Reason :
Oxidation state of $Cr$ in ${Na}_{2} {CrO}_{4}$ is $+ VI$ .

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:

${Na}_{2} {CrO}_{4}$ solution in water is yellow in colour, when acidified it changes to orange colour (due to the formation of ${Cr}_{2} O_{7}^{2 -}$ ions).
$2 {Na}_{2} {Cr}_{2} O_{4} + H_{2} {SO}_{4} \to$
${Na}_{2} {Cr}_{2} O_{7} + {Na}_{2} {SO}_{4} + H_{2} O$
Let oxidation state of $Cr$ in ${Na}_{2} {Cr}_{2} O_{4}$ be x.
$\Rightarrow 2 (+ 1) + x + 4 (- 2) = 0 \Rightarrow x = + 6$ .
So option (2) is correct.

CHXII08:THE D- & F-BLOCK ELEMENTS

321283 The number of $Cr - O - Cr$ bonds in dichromate ion is ____ .

1 1

2 0

3 2

4 3

CHXII08:THE D- & F-BLOCK ELEMENTS

321279 ${CrO}_{3}$ dissolves in aq. NaOH to give

1

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

2

Cr (OH)_{2}

3

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

4

Cr (OH)_{3}

Explanation:

${CrO}_{3} + 2 {OH}^{-} \to {CrO}_{4}^{- 2} + H_{2} O$

CHXII08:THE D- & F-BLOCK ELEMENTS

321280 Assertion :
Solution of ${Na}_{2} {CrO}_{4}$ in water is intensely coloured.
Reason :
Oxidation state of $Cr$ in ${Na}_{2} {CrO}_{4}$ is $(+ VI)$ .

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 Both Assertion and Reason is incorrect.

Explanation:

In $N a_{2} Cr O_{4},$ is in +6 oxidation state with $d^{\circ}$ configuration. The ${CrO}_{4}^{2 -}$ ions in aqueous solution give yellow colour which is not due to $d - d$ transition but due to charge transfer, i.e., momentary transfer of charge from oxygen atom to metal atom.
Hence, both Assertion and Reason are correct but Reason is not the correct explanation of Assertion.

AIIMS - 2013

CHXII08:THE D- & F-BLOCK ELEMENTS

321281 Potassium dichromate acts as a strong oxidising agent in acidic solution. During this process, the oxidation state changes from

1

+ 6

to

+ 3

2

+ 3

to

+ 1

3

+ 6

to

+ 2

4

+ 2

to

+ 1

Explanation:

In acidic medium,
$\overset{+ 6}{{Cr}_{2}} O_{7}^{2 -} + 14 H^{+} + 6 e^{-} \to 2 {Cr}^{+ 3} + 7 H_{2} O$
The oxidation state changes from $+ 6$ to $+ 3$ .

JEE - 2023

CHXII08:THE D- & F-BLOCK ELEMENTS

321282 Assertion :
Solution of ${Na}_{2} {CrO}_{4}$ in water is intensely coloured.
Reason :
Oxidation state of $Cr$ in ${Na}_{2} {CrO}_{4}$ is $+ VI$ .

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:

${Na}_{2} {CrO}_{4}$ solution in water is yellow in colour, when acidified it changes to orange colour (due to the formation of ${Cr}_{2} O_{7}^{2 -}$ ions).
$2 {Na}_{2} {Cr}_{2} O_{4} + H_{2} {SO}_{4} \to$
${Na}_{2} {Cr}_{2} O_{7} + {Na}_{2} {SO}_{4} + H_{2} O$
Let oxidation state of $Cr$ in ${Na}_{2} {Cr}_{2} O_{4}$ be x.
$\Rightarrow 2 (+ 1) + x + 4 (- 2) = 0 \Rightarrow x = + 6$ .
So option (2) is correct.

CHXII08:THE D- & F-BLOCK ELEMENTS

321283 The number of $Cr - O - Cr$ bonds in dichromate ion is ____ .

1 1

2 0

3 2

4 3

CHXII08:THE D- & F-BLOCK ELEMENTS

321279 ${CrO}_{3}$ dissolves in aq. NaOH to give

1

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

2

Cr (OH)_{2}

3

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

4

Cr (OH)_{3}

Explanation:

${CrO}_{3} + 2 {OH}^{-} \to {CrO}_{4}^{- 2} + H_{2} O$

CHXII08:THE D- & F-BLOCK ELEMENTS

321280 Assertion :
Solution of ${Na}_{2} {CrO}_{4}$ in water is intensely coloured.
Reason :
Oxidation state of $Cr$ in ${Na}_{2} {CrO}_{4}$ is $(+ VI)$ .

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 Both Assertion and Reason is incorrect.

Explanation:

In $N a_{2} Cr O_{4},$ is in +6 oxidation state with $d^{\circ}$ configuration. The ${CrO}_{4}^{2 -}$ ions in aqueous solution give yellow colour which is not due to $d - d$ transition but due to charge transfer, i.e., momentary transfer of charge from oxygen atom to metal atom.
Hence, both Assertion and Reason are correct but Reason is not the correct explanation of Assertion.

AIIMS - 2013

CHXII08:THE D- & F-BLOCK ELEMENTS

321281 Potassium dichromate acts as a strong oxidising agent in acidic solution. During this process, the oxidation state changes from

1

+ 6

to

+ 3

2

+ 3

to

+ 1

3

+ 6

to

+ 2

4

+ 2

to

+ 1

Explanation:

In acidic medium,
$\overset{+ 6}{{Cr}_{2}} O_{7}^{2 -} + 14 H^{+} + 6 e^{-} \to 2 {Cr}^{+ 3} + 7 H_{2} O$
The oxidation state changes from $+ 6$ to $+ 3$ .

JEE - 2023

CHXII08:THE D- & F-BLOCK ELEMENTS

321282 Assertion :
Solution of ${Na}_{2} {CrO}_{4}$ in water is intensely coloured.
Reason :
Oxidation state of $Cr$ in ${Na}_{2} {CrO}_{4}$ is $+ VI$ .

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:

${Na}_{2} {CrO}_{4}$ solution in water is yellow in colour, when acidified it changes to orange colour (due to the formation of ${Cr}_{2} O_{7}^{2 -}$ ions).
$2 {Na}_{2} {Cr}_{2} O_{4} + H_{2} {SO}_{4} \to$
${Na}_{2} {Cr}_{2} O_{7} + {Na}_{2} {SO}_{4} + H_{2} O$
Let oxidation state of $Cr$ in ${Na}_{2} {Cr}_{2} O_{4}$ be x.
$\Rightarrow 2 (+ 1) + x + 4 (- 2) = 0 \Rightarrow x = + 6$ .
So option (2) is correct.

CHXII08:THE D- & F-BLOCK ELEMENTS

321283 The number of $Cr - O - Cr$ bonds in dichromate ion is ____ .

1 1

2 0

3 2

4 3

CHXII08:THE D- & F-BLOCK ELEMENTS

321279 ${CrO}_{3}$ dissolves in aq. NaOH to give

1

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

2

Cr (OH)_{2}

3

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

4

Cr (OH)_{3}

Explanation:

${CrO}_{3} + 2 {OH}^{-} \to {CrO}_{4}^{- 2} + H_{2} O$

CHXII08:THE D- & F-BLOCK ELEMENTS

321280 Assertion :
Solution of ${Na}_{2} {CrO}_{4}$ in water is intensely coloured.
Reason :
Oxidation state of $Cr$ in ${Na}_{2} {CrO}_{4}$ is $(+ VI)$ .

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 Both Assertion and Reason is incorrect.

Explanation:

In $N a_{2} Cr O_{4},$ is in +6 oxidation state with $d^{\circ}$ configuration. The ${CrO}_{4}^{2 -}$ ions in aqueous solution give yellow colour which is not due to $d - d$ transition but due to charge transfer, i.e., momentary transfer of charge from oxygen atom to metal atom.
Hence, both Assertion and Reason are correct but Reason is not the correct explanation of Assertion.

AIIMS - 2013

CHXII08:THE D- & F-BLOCK ELEMENTS

321281 Potassium dichromate acts as a strong oxidising agent in acidic solution. During this process, the oxidation state changes from

1

+ 6

to

+ 3

2

+ 3

to

+ 1

3

+ 6

to

+ 2

4

+ 2

to

+ 1

Explanation:

In acidic medium,
$\overset{+ 6}{{Cr}_{2}} O_{7}^{2 -} + 14 H^{+} + 6 e^{-} \to 2 {Cr}^{+ 3} + 7 H_{2} O$
The oxidation state changes from $+ 6$ to $+ 3$ .

JEE - 2023

CHXII08:THE D- & F-BLOCK ELEMENTS

321282 Assertion :
Solution of ${Na}_{2} {CrO}_{4}$ in water is intensely coloured.
Reason :
Oxidation state of $Cr$ in ${Na}_{2} {CrO}_{4}$ is $+ VI$ .

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:

${Na}_{2} {CrO}_{4}$ solution in water is yellow in colour, when acidified it changes to orange colour (due to the formation of ${Cr}_{2} O_{7}^{2 -}$ ions).
$2 {Na}_{2} {Cr}_{2} O_{4} + H_{2} {SO}_{4} \to$
${Na}_{2} {Cr}_{2} O_{7} + {Na}_{2} {SO}_{4} + H_{2} O$
Let oxidation state of $Cr$ in ${Na}_{2} {Cr}_{2} O_{4}$ be x.
$\Rightarrow 2 (+ 1) + x + 4 (- 2) = 0 \Rightarrow x = + 6$ .
So option (2) is correct.

CHXII08:THE D- & F-BLOCK ELEMENTS

321283 The number of $Cr - O - Cr$ bonds in dichromate ion is ____ .

1 1

2 0

3 2

4 3