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CHXI11:THE P-BLOCK ELEMENTS

316065 In the structure of Borax, how many $σ$ bonds and no. of lone pairs present respectively?

1 30, 34

2 34, 34

3 32, 34

4 34, 30

CHXI11:THE P-BLOCK ELEMENTS

316066 An aqueous solution of borax is

1 Neutral

2 Amphoteric

3 Basic

4 Acidic

Explanation:

Borax is a salt of WA and SB. Hence this salt undergoes anionic hydrolysis resulting basic solution.
${Na}_{2} B_{4} O_{7} + 7 H_{2} O \to 2 NaOH + 4 H_{3} {BO}_{3} .$
Since $NaOH$ is a strong base, the solution will be alkaline in nature.

CHXI11:THE P-BLOCK ELEMENTS

316067 $N a_{2} B_{4} O_{7} \cdot 10 H_{2} O \overset{Δ}{\to} X + NaB O_{2} + H_{2} O$
$X + C r_{2} O_{3} \overset{Δ}{\to} Y$ (green colored)
The $X$ and $Y$ are

1

N a_{3} B O_{3} &  Cr {(B O_{2})}_{3}

2

N a_{2} B_{4} O_{7} &  Cr {(B O_{2})}_{3}

3

B_{2} O_{3} &  Cr {(B O_{2})}_{3}

4

B_{2} O_{3} &  CrB O_{3}

Explanation:

$N a_{2} B_{4} O_{7} .10 H_{2} O \overset{Δ}{\to} \underset{(x)}{B_{2} O_{3}} + 2NaB O_{2} + 10 H_{2} O$
$3 B_{2} O_{3} + C r_{2} O_{3} \overset{Δ}{\to} \underset{(y)}{2Cr} {(B O_{2})}_{3}$

CHXI11:THE P-BLOCK ELEMENTS

316068 Which of the following can be detected by the borax-bead test?

1

{Ni}^{2 +}

2

{Co}^{2 +}

3

{Pb}^{+ 2}

4 Both (1) & (2)

CHXI11:THE P-BLOCK ELEMENTS

316069 During the borax bead test with ${CuSO}_{4}$ , a blue green colour of the bead was observed in oxidising flame due to the formation of

1

{Cu}_{3} B_{2}

2

Cu {({BO}_{2})}_{2}

3 CuO

4 Cu

Explanation:

When ${CuSO}_{4}$ is heated on a loop of Pt wire with borax, blue green coloured $Cu {({BO}_{2})}_{2}$ bead is formed.
$CuS O_{4} \overset{Δ}{\to} CuO + S O_{3}$
$CuO + B_{2} O_{3} \to \underset{Blue - green colour}{Cu {(B O_{2})}_{2}}$

JEE - 2023

CHXI11:THE P-BLOCK ELEMENTS

316065 In the structure of Borax, how many $σ$ bonds and no. of lone pairs present respectively?

1 30, 34

2 34, 34

3 32, 34

4 34, 30

CHXI11:THE P-BLOCK ELEMENTS

316066 An aqueous solution of borax is

1 Neutral

2 Amphoteric

3 Basic

4 Acidic

Explanation:

Borax is a salt of WA and SB. Hence this salt undergoes anionic hydrolysis resulting basic solution.
${Na}_{2} B_{4} O_{7} + 7 H_{2} O \to 2 NaOH + 4 H_{3} {BO}_{3} .$
Since $NaOH$ is a strong base, the solution will be alkaline in nature.

CHXI11:THE P-BLOCK ELEMENTS

316067 $N a_{2} B_{4} O_{7} \cdot 10 H_{2} O \overset{Δ}{\to} X + NaB O_{2} + H_{2} O$
$X + C r_{2} O_{3} \overset{Δ}{\to} Y$ (green colored)
The $X$ and $Y$ are

1

N a_{3} B O_{3} &  Cr {(B O_{2})}_{3}

2

N a_{2} B_{4} O_{7} &  Cr {(B O_{2})}_{3}

3

B_{2} O_{3} &  Cr {(B O_{2})}_{3}

4

B_{2} O_{3} &  CrB O_{3}

Explanation:

$N a_{2} B_{4} O_{7} .10 H_{2} O \overset{Δ}{\to} \underset{(x)}{B_{2} O_{3}} + 2NaB O_{2} + 10 H_{2} O$
$3 B_{2} O_{3} + C r_{2} O_{3} \overset{Δ}{\to} \underset{(y)}{2Cr} {(B O_{2})}_{3}$

CHXI11:THE P-BLOCK ELEMENTS

316068 Which of the following can be detected by the borax-bead test?

1

{Ni}^{2 +}

2

{Co}^{2 +}

3

{Pb}^{+ 2}

4 Both (1) & (2)

CHXI11:THE P-BLOCK ELEMENTS

316069 During the borax bead test with ${CuSO}_{4}$ , a blue green colour of the bead was observed in oxidising flame due to the formation of

1

{Cu}_{3} B_{2}

2

Cu {({BO}_{2})}_{2}

3 CuO

4 Cu

Explanation:

When ${CuSO}_{4}$ is heated on a loop of Pt wire with borax, blue green coloured $Cu {({BO}_{2})}_{2}$ bead is formed.
$CuS O_{4} \overset{Δ}{\to} CuO + S O_{3}$
$CuO + B_{2} O_{3} \to \underset{Blue - green colour}{Cu {(B O_{2})}_{2}}$

JEE - 2023

CHXI11:THE P-BLOCK ELEMENTS

316065 In the structure of Borax, how many $σ$ bonds and no. of lone pairs present respectively?

1 30, 34

2 34, 34

3 32, 34

4 34, 30

CHXI11:THE P-BLOCK ELEMENTS

316066 An aqueous solution of borax is

1 Neutral

2 Amphoteric

3 Basic

4 Acidic

Explanation:

Borax is a salt of WA and SB. Hence this salt undergoes anionic hydrolysis resulting basic solution.
${Na}_{2} B_{4} O_{7} + 7 H_{2} O \to 2 NaOH + 4 H_{3} {BO}_{3} .$
Since $NaOH$ is a strong base, the solution will be alkaline in nature.

CHXI11:THE P-BLOCK ELEMENTS

316067 $N a_{2} B_{4} O_{7} \cdot 10 H_{2} O \overset{Δ}{\to} X + NaB O_{2} + H_{2} O$
$X + C r_{2} O_{3} \overset{Δ}{\to} Y$ (green colored)
The $X$ and $Y$ are

1

N a_{3} B O_{3} &  Cr {(B O_{2})}_{3}

2

N a_{2} B_{4} O_{7} &  Cr {(B O_{2})}_{3}

3

B_{2} O_{3} &  Cr {(B O_{2})}_{3}

4

B_{2} O_{3} &  CrB O_{3}

Explanation:

$N a_{2} B_{4} O_{7} .10 H_{2} O \overset{Δ}{\to} \underset{(x)}{B_{2} O_{3}} + 2NaB O_{2} + 10 H_{2} O$
$3 B_{2} O_{3} + C r_{2} O_{3} \overset{Δ}{\to} \underset{(y)}{2Cr} {(B O_{2})}_{3}$

CHXI11:THE P-BLOCK ELEMENTS

316068 Which of the following can be detected by the borax-bead test?

1

{Ni}^{2 +}

2

{Co}^{2 +}

3

{Pb}^{+ 2}

4 Both (1) & (2)

CHXI11:THE P-BLOCK ELEMENTS

316069 During the borax bead test with ${CuSO}_{4}$ , a blue green colour of the bead was observed in oxidising flame due to the formation of

1

{Cu}_{3} B_{2}

2

Cu {({BO}_{2})}_{2}

3 CuO

4 Cu

Explanation:

When ${CuSO}_{4}$ is heated on a loop of Pt wire with borax, blue green coloured $Cu {({BO}_{2})}_{2}$ bead is formed.
$CuS O_{4} \overset{Δ}{\to} CuO + S O_{3}$
$CuO + B_{2} O_{3} \to \underset{Blue - green colour}{Cu {(B O_{2})}_{2}}$

JEE - 2023

CHXI11:THE P-BLOCK ELEMENTS

316065 In the structure of Borax, how many $σ$ bonds and no. of lone pairs present respectively?

1 30, 34

2 34, 34

3 32, 34

4 34, 30

CHXI11:THE P-BLOCK ELEMENTS

316066 An aqueous solution of borax is

1 Neutral

2 Amphoteric

3 Basic

4 Acidic

Explanation:

Borax is a salt of WA and SB. Hence this salt undergoes anionic hydrolysis resulting basic solution.
${Na}_{2} B_{4} O_{7} + 7 H_{2} O \to 2 NaOH + 4 H_{3} {BO}_{3} .$
Since $NaOH$ is a strong base, the solution will be alkaline in nature.

CHXI11:THE P-BLOCK ELEMENTS

316067 $N a_{2} B_{4} O_{7} \cdot 10 H_{2} O \overset{Δ}{\to} X + NaB O_{2} + H_{2} O$
$X + C r_{2} O_{3} \overset{Δ}{\to} Y$ (green colored)
The $X$ and $Y$ are

1

N a_{3} B O_{3} &  Cr {(B O_{2})}_{3}

2

N a_{2} B_{4} O_{7} &  Cr {(B O_{2})}_{3}

3

B_{2} O_{3} &  Cr {(B O_{2})}_{3}

4

B_{2} O_{3} &  CrB O_{3}

Explanation:

$N a_{2} B_{4} O_{7} .10 H_{2} O \overset{Δ}{\to} \underset{(x)}{B_{2} O_{3}} + 2NaB O_{2} + 10 H_{2} O$
$3 B_{2} O_{3} + C r_{2} O_{3} \overset{Δ}{\to} \underset{(y)}{2Cr} {(B O_{2})}_{3}$

CHXI11:THE P-BLOCK ELEMENTS

316068 Which of the following can be detected by the borax-bead test?

1

{Ni}^{2 +}

2

{Co}^{2 +}

3

{Pb}^{+ 2}

4 Both (1) & (2)

CHXI11:THE P-BLOCK ELEMENTS

316069 During the borax bead test with ${CuSO}_{4}$ , a blue green colour of the bead was observed in oxidising flame due to the formation of

1

{Cu}_{3} B_{2}

2

Cu {({BO}_{2})}_{2}

3 CuO

4 Cu

Explanation:

When ${CuSO}_{4}$ is heated on a loop of Pt wire with borax, blue green coloured $Cu {({BO}_{2})}_{2}$ bead is formed.
$CuS O_{4} \overset{Δ}{\to} CuO + S O_{3}$
$CuO + B_{2} O_{3} \to \underset{Blue - green colour}{Cu {(B O_{2})}_{2}}$

JEE - 2023

CHXI11:THE P-BLOCK ELEMENTS

316065 In the structure of Borax, how many $σ$ bonds and no. of lone pairs present respectively?

1 30, 34

2 34, 34

3 32, 34

4 34, 30

CHXI11:THE P-BLOCK ELEMENTS

316066 An aqueous solution of borax is

1 Neutral

2 Amphoteric

3 Basic

4 Acidic

Explanation:

Borax is a salt of WA and SB. Hence this salt undergoes anionic hydrolysis resulting basic solution.
${Na}_{2} B_{4} O_{7} + 7 H_{2} O \to 2 NaOH + 4 H_{3} {BO}_{3} .$
Since $NaOH$ is a strong base, the solution will be alkaline in nature.

CHXI11:THE P-BLOCK ELEMENTS

316067 $N a_{2} B_{4} O_{7} \cdot 10 H_{2} O \overset{Δ}{\to} X + NaB O_{2} + H_{2} O$
$X + C r_{2} O_{3} \overset{Δ}{\to} Y$ (green colored)
The $X$ and $Y$ are

1

N a_{3} B O_{3} &  Cr {(B O_{2})}_{3}

2

N a_{2} B_{4} O_{7} &  Cr {(B O_{2})}_{3}

3

B_{2} O_{3} &  Cr {(B O_{2})}_{3}

4

B_{2} O_{3} &  CrB O_{3}

Explanation:

$N a_{2} B_{4} O_{7} .10 H_{2} O \overset{Δ}{\to} \underset{(x)}{B_{2} O_{3}} + 2NaB O_{2} + 10 H_{2} O$
$3 B_{2} O_{3} + C r_{2} O_{3} \overset{Δ}{\to} \underset{(y)}{2Cr} {(B O_{2})}_{3}$

CHXI11:THE P-BLOCK ELEMENTS

316068 Which of the following can be detected by the borax-bead test?

1

{Ni}^{2 +}

2

{Co}^{2 +}

3

{Pb}^{+ 2}

4 Both (1) & (2)

CHXI11:THE P-BLOCK ELEMENTS

316069 During the borax bead test with ${CuSO}_{4}$ , a blue green colour of the bead was observed in oxidising flame due to the formation of

1

{Cu}_{3} B_{2}

2

Cu {({BO}_{2})}_{2}

3 CuO

4 Cu

Explanation:

When ${CuSO}_{4}$ is heated on a loop of Pt wire with borax, blue green coloured $Cu {({BO}_{2})}_{2}$ bead is formed.
$CuS O_{4} \overset{Δ}{\to} CuO + S O_{3}$
$CuO + B_{2} O_{3} \to \underset{Blue - green colour}{Cu {(B O_{2})}_{2}}$

JEE - 2023

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