Chemistry

Chemical Reactions and Equations

684 Questions

Chemical reactions and equations form a foundational chemistry topic where students identify reaction products, balance chemical formulas, and classify reaction types. It covers critical mechanisms like Markovnikov's rule, precipitation, and endothermic or exothermic processes. These questions are highly common in general science sections of state and central government competitive exams.

Endothermic reactionsPrecipitation reactionsDehydrohalogenation of alkyl halidesChemical equation balancingReaction product identification

Chemical Reactions and Equations Questions

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

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:

  1. $-3$
  2. $+3$
  3. $+5$
  4. $0$
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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:

  1. $0$
  2. $+1$
  3. $+3$
  4. $-3$
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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

  1. Aniline

  2. Phenol

  3. Anisole

  4. Nitrobenzene
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

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

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?

  1. 1

  2. 2

  3. 3

  4. 4
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

For successful diazotization, 3 moles of mineral acid are required per mole of amine: 1 mole to convert the amine to its salt, 1 mole to generate nitrous acid from sodium nitrite, and 1 mole to maintain a highly acidic medium to prevent coupling reactions.

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

Reaction at ${ 0-5 }^{ 0 }C$ between aniline, ${ NaNO } { 2 }$ and HCl is known as___________

  1. Suphonation of benzene

  2. Acylation of aniline

  3. Alkylation of aniline

  4. Diazotisation
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

This is the diazotization reaction.


The reaction goes as follows :
$PhNH _{2} + NaNO _{2} + HCl \rightarrow PhN _{2}^{+} Cl^{-}$

The benzendiazonium salt thus formed acts as a synthetic intermediate and can be used to synthesize a wide variety of substituted benzene compounds.

For example,
$PhN _{2}^{+} Cl^{-} + CuCN \rightarrow PhCN$ (cyanobenzene)
$PhN _{2}^{+} Cl^{-} + CuI (KI) \rightarrow PhI$ (iodobenzene)

Option D is correct.

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

Aniline when treated with $NaNO { 2 }$ and $HCl$ at $0- { 5 }^{ 0 }C$ gives ___________ as a product.

  1. chloroaniline

  2. benzene diazonium chloride

  3. chlorobenzene

  4. dichlorobenzene
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Aniline reacts with sodium nitrite and HCl in cold condition to form benzene diazonium chloride.
$\underset {aniline} {{ C } _{ 6 }{ H } _{ 5 }{ NH } _{ 2 }}\xrightarrow [ { NaNO } _{ 2 } ]{ HCl } \underset {benzene diazonium chloride} {[C _6H _5-N _2^+Cl^-]}$

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

Diazomethane was photolysed to generate singlet carbine which was treated with cis-2-butene. The main product(s) of the reaction is/are:

  1. cis-1, 2-dimethylcyclopropane

  2. trans-1, 2-dimethylcyclopropane
  3. mixture of $(A)$ and $(B)$

  4. Ethylcyclopropane
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Solution:- (A) cis-$1,2$-dimethylcyclopropane

$\underset{\text{Diazomethane}}{C{H} _{2}-\overset{+}{N}={N}^{-}} \xrightarrow[-N \equiv N]{h \nu} \underset{\text{Singlet carbene} \left( \text{Methylene} \right)}{:C{H} _{2}}$
The addition of methylene would yield trans-$1,2$-dimethylcyclopropane from trans-$2$-butene and cis-$1,2$-dimethylcyclopropane from cis-$2$-butene.

Multiple choice

Carbon

  1. Ca

  2. C

  3. Co

  4. Cn
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Carbon is represented by the chemical symbol C. Ca is the symbol for calcium, and Co is the symbol for cobalt.