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Questions Related to chemistry

When excess of ammonia is used:


 $3Cl _2+8NH _3$$\longrightarrow$$A+B$

When excess of chlorine is used:

$3Cl _2+4NH _3$$\longrightarrow$$C+D$

The oxidation state of nitrogen in compound $A$ is:

chemistry nitrogen and sulfur ammonia-properties and uses ammonia compounds of nitrogen - ammonia

  1. $-3$

  2. $+3$

  3. $+5$

  4. $0$

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Correct Option: A
Explanation:

$8 NH _3 + 3 Cl _2 \rightarrow  6 NH _4Cl+N _2$

 Compound A is $NH _4Cl$ 

$1(x)+4(1)+1(-1)=0$

$x+4-1=0$

$x=-3$

The oxidation state of compound A is $-3$

Hence option A is correct.

When excess of ammonia is used:
 $3Cl _2+8NH _3$$\longrightarrow$$A+B$
When access of chlorine is used:
$3Cl _2+4NH _3$$\longrightarrow$$C+D$
Oxidation state of nitrogen in compound $B$ is:

chemistry nitrogen and sulfur ammonia-properties and uses ammonia compounds of nitrogen - ammonia

  1. $0$

  2. $+1$

  3. $+3$

  4. $-3$

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Correct Option: A
Explanation:

$8 NH _3 + 3 Cl _2 \rightarrow  6 NH _4Cl+N _2$

$3Cl _2+4NH _3 \rightarrow  3NH _4Cl+NCl _3$

 Compound  B is $N _2$ Here as the nitrogen is in elemental state so its oxidation state is $0$

 Hence option A is correct.

Which of the following compounds will not undergo azo coupling reaction with benzene diazonium chloride?

chemistry amines introduction to diazonium salts structure, preparation and physical properties of diazonium salts diazonium salts

  1. Aniline

  2. Phenol

  3. Anisole

  4. Nitrobenzene

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Correct Option: D
Explanation:

Diazonium cation is weak electrophile and hence it reacts with electron rich compounds containing electron donating groups such as $-OH$, $-NH _2$ and $OCH _3$ groups and not with compounds containing electron withdrawing groups such as $-NO _2$ etc.


Hence,option D is correct.

Which of the following diazonium salt is relatively stable of $0-5^o$C?

chemistry amines introduction to diazonium salts structure, preparation and physical properties of diazonium salts diazonium salts

  1. $CH _3CH _2N\equiv N}^{\oplus}Cl^-$

  2. $CH _3-C(CH _3) _2-N\equiv N}^{\oplus} Cl^-$

  3. $CH _3-N\equiv N}^{\oplus}Cl^-$

  4. $(CH _3) _3C-N\equiv N}^{\oplus}Cl^-$

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Correct Option: C

Which of the following diazonium salt is relatively stable at $0-{ 5^0 }^{ }C$?

chemistry amines introduction to diazonium salts structure, preparation and physical properties of diazonium salts diazonium salts

  1. ${ CH } _{ 3 }-N\equiv N{ } }^{ \oplus }C{ l }^{ - }$

  2. ${ \left( { CH } _{ 3 } \right) } _{ 2 }CH-N\equiv N{ } }^{ \oplus }{ Cl }^{ - }$

  3. ${ C } _{ 6 }{ H } _{ 5 }-N\equiv N{ } }^{ \oplus }{ Cl }^{ - }$

  4. ${ \left( { CH } _{ 3 } \right) } _{ 3 }C-N\equiv N{ } }^{ \oplus }{ Cl }^{ - }$

Show answer
Correct Option: D
Explanation:

The $+I$ effect which stabilizes the ${ N }^{ + }$ion is in the following order ${ C } _{ 6 }{ H } _{ 5 }-<{ CH } _{ 3 }-<{ \left( { CH } _{ 3 } \right)  } _{ 2 }-<{ \left( { CH } _{ 3 } \right)  } _{ 3 }$

$\therefore $ The ${ \left{ { \left( { CH } _{ 3 } \right)  } _{ 3 }C-N\equiv N \right}  }^{ + }{ Cl }^{ - }$ is most stable

Which of the following is an Incorrect statement about benzenediazonium chloride?

chemistry amines introduction to diazonium salts structure, preparation and physical properties of diazonium salts diazonium salts

  1. It is prepared by the reaction of aniline with nitrous acid at 273-278 K

  2. It is a colourless crystalline solid

  3. Alkyl diazonium salts are more stable than arenediazonium salts

  4. Benzene diazonium fluoroborate is water insoluble & stable at room temperature

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Correct Option: C

For the successful diazotisation of arylamines, how many mole of mineral acid $(HCl \quad or \quad H _2SO _4 )$ are required for each mole of the amine?

chemistry amines introduction to diazonium salts structure, preparation and physical properties of diazonium salts diazonium salts

  1. 1

  2. 2

  3. 3

  4. 4

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Correct Option: C

In an analytical determination of arsenic, a solution containing arsenious acid, $ H _{3}AsO _{4},$ KI and a small amount of starch is electrolysed. The electrolysis produces free $I _{2}$ from $ I^{-}$ ions and the $ I _{2}$ immediately oxidizes the arsenious acid to hydrogen arsenate ion, $ HAsO _{4}^{2-}.$
$ I _{2}+H _{3}AsO _{3}+H _{2}O \rightarrow 2I^{-} + HAsO _{4}^{2-}+4H^{+}$
When the oxidation of arsenic is complete, the free iodine blue colour. If during a particular run, it takes 96.5 s for a current of 10.0 mA to give an end point (indicated by the blue colour),how many g of arsenic are present in the solution. (As = 75)

chemistry amines introduction to diazonium salts structure, preparation and physical properties of diazonium salts diazonium salts

  1. $ 6.3 \times 10^{-4} g$

  2. $1.26 \times 10^{-4}g$

  3. $ 3.15 \times 10^{-5}g$

  4. $ 6.3 \times 10^{-5}g$

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Correct Option: D

State, whether the following statements are True or False:
Aniline forms phenol when treated with nitrous acid.

chemistry amines introduction to diazonium salts structure, preparation and physical properties of diazonium salts diazonium salts

  1. True

  2. False

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Correct Option: B

Which of the following amines form unstable diazonium salt?

chemistry amines introduction to diazonium salts structure, preparation and physical properties of diazonium salts diazonium salts

  1. ${ C } _{ 6 }{ H } _{ 5 }{ NH } _{ 2 }$

  2. $\left( { C } _{ 2 }{ H } _{ 5 } \right) _{ 2 }NH$

  3. $\left( { C } _{ 2 }{ H } _{ 5 } \right) _{ 3 }N$

  4. ${ CH } _{ 3 }{ NHC } _{ 2 }{ H } _{ 5 }$

Show answer
Correct Option: B,C,D
Explanation:

Only primary aromatic amines form stable arene diazonium salts.
The reaction is as follows:

$C _{6}H _{5}NH _{2} + NaNO _{2} + HCl (0-5^{\circ}C) \rightarrow PhN _{2}^{+}Cl^{-}$

Remain forms the unstable diazonium salt.
So, the correct options are $B$, $C$, $D$