Chemistry

Chemical Reactions and Equations

674 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 zoology gas exchange and smoking respiration in human beings respiration and associated structures respiration in humans respiratory organs in humans

Complete and balance the following equation $Na _2HPO _4+X\rightarrow Y+NaH _2PO _4$.

  1. $X=NaHCO _3, Y=NaCl$
  2. $X=NaHCO _3, Y=H _2CO _3$
  3. $X=H _2CO _3, Y=NaH _2CO _3$
  4. $X=H _2CO _3, Y=NaHCO _3$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The reaction Na2HPO4 + H2CO3 -> NaHCO3 + NaH2PO4 is a standard buffer reaction where carbonic acid reacts with disodium hydrogen phosphate to form sodium bicarbonate and sodium dihydrogen phosphate.

Multiple choice urea organic compounds with functional group containing nitrogen

$NH 2COONH _4 \rightleftharpoons $ ____________.

  1. $NH _2CONH _2$, $H _2O$
  2. $NH _2CONH _2$
  3. $NH _2COONH _2$, $NH _2CONH _2$
  4. $NH _2COONH _2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The basic process, developed in 1922, is also called the Bosch–Meiser urea process after its discoverers. Various commercial urea processes are characterized by the conditions under which urea forms and the way that unconverted reactants are further processed. The process consists of two main equilibrium reactions, with incomplete conversion of the reactants. 

The second is urea conversion: the slower endothermic decomposition of ammonium carbamate into urea and water:

${ H } _{ 2 }N-COON{ H } _{ 4 }⇌{ (N{ H } _{ 2 }) } _{ 2 }CO+{ H } _{ 2 }O$

Multiple choice urea organic compounds with functional group containing nitrogen

First step of urea manufacture is $2NH _3 \ + \ CO _2 \rightleftharpoons X$
Compound $X$ is:

  1. $NH _2COONH _4$
  2. $NH _2COOH$
  3. $NH _4COOH$
  4. Both $A$ and $B$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The first is carbamate formation: the fast exothermic reaction of liquid ammonia with gaseous carbon dioxide at high temperature and pressure to form ammonium carbamate (${ H } _{ 2 }N-COO-N{ H } _{ 4 }$).

 $2N{ H } _{ 3 }+C{ O } _{ 2 }\rightleftharpoons { H } _{ 2 }N-COO-N{ H } _{ 4 }$

Multiple choice chemistry organic nitrogen compounds nitroarenes- preparation and properties nitro compounds types of organic reactions

What is obtained when nitrobenzene is treated sequentially with (i) ${ NH } _{ 4 }Cl/Zn$ dust and (ii) ${ H } _{ 2 }{ SO } _{ 4 }/{ Na } _{ 2 }{ Cr } _{ 2 }{ O } _{ 7 }$ ?

  1. Benzene

  2. Nitrosobenzene

  3. m-Chlorobenzene

  4. p-Chlorobenzene
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When Nitrobenzene first reacts with $NH _4Cl/Zn$ it forms phenyl hydroxylamine.

When this reacts with $H _2SO _4/ Na _2Cr _2O _7$ it gives Nitroso benzene as a product.

Multiple choice chemistry organic nitrogen compounds nitroarenes- preparation and properties nitro compounds types of organic reactions

Benzene on reaction with conc. $HNO _{3}$ in presence of conc. $H _{2}SO _{4}$ followed by the treatment of $Cl _{2}$ in presence of $FeCl _{3}$, it gives :

  1. $2 - chloro - 1 - nitrobenzene$
  2. $1 - chloro - 3- nitrobenzene$
  3. $3 - chloro - 1- nitrobenzene$
  4. A mixture of $2 - chloro$ and $4 - chloro - 1 - nitrobenzene$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

3-Chloro-1-nitrobenzene
Nitro substituents have positive charge on the atom bonded to ring. So the like charges repel each other at ortho and para position as compared to meta substitution. So meta position is favored at 3 chloro in the ring.

Multiple choice chemistry organic nitrogen compounds nitroarenes- preparation and properties nitro compounds types of organic reactions

When nitrobenzene is treated with $Br _{2}$ in presence of $FeBr _{3}$ the major product formed is m - bromonitrobensene. Statement which is related to obtain the m - isomer is:

  1. The electron density of meta carbon is more than that on ortho and para positions
  2. Loss of aromaticity when $Br^{+}$ attacks at the ortho and para positions and not at meta position
  3. Easier loss of $H^{+}$ to regain aromaticity from the meta position than from ortho and para positions

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The exact influence of a given substituent is seen as its interactions with the delocalized positive charge on the benzonium intermediate generated by bonding to the electrophile at each of the three substitution sites. Nitro groups have a positive charge on the atom bonded to the aromatic ring. Like charges of two groups are destabilized by charge repulsion so meta-products predominate as compared to others.

Multiple choice chemistry occurrence of carbon compounds in nature importance of carbon covalent bonding in carbon compounds carbon and its forms

The reaction between carbon and oxygen can be represented as 
$C _{(s)}+O _{2(x)}\rightarrow CO _{2(g)}+heat$
In which of the following type(s), the above reaction can be classified?
I. Combustion reaction
II. Displacement reaction
III. Endothermic reaction
IV. Combination reaction

  1. (I) and (III)

  2. (I), (II) and (IV)

  3. (I) and (IV)

  4. (I) only
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$C _{(s)}+O _{2(g)}\rightarrow CO _{2(g)}+heat$
It is combination and combustion reaction.

Multiple choice chemistry chemical kinetics introduction to chemical kinetics understanding chemical kinetics rate of chemical reaction
Find out the correct order of rate of reaction towards allylic substitution :
(I) $CH _3 - CH = CH _2$
(II) $CH _3 -CH _2 - CH = CH _2$
(III) $CH _3 - \overset{CH _3}{\overset{\!\!\!\!\!\!|}{CH}} - CH = CH _2$
  1. ${\rm{I}}\,\,{\rm{ > }}\,\,{\rm{II}}\,\,{\rm{ > }}\,\,{\rm{III}}$
  2. ${\rm{II}}\,\,{\rm{ > }}\,\,{\rm{I}}\,\,{\rm{ > }}\,\,{\rm{III}}$
  3. ${\rm{III}}\,\,{\rm{ > }}\,\,{\rm{I}}\,\,{\rm{ > }}\,\,{\rm{II}}$
  4. ${\rm{III}}\,\,{\rm{ > }}\,\,{\rm{II}}\,\,{\rm{ > }}\,\,{\rm{I}}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Allylic substitution proceeds via free radical formation, and stability follows tertiary > secondary > primary free radicals. Structure III has a tertiary allylic hydrogen, structure II has a secondary one, and structure I has a primary one. Thus, the rate of reaction is highest for III and lowest for I.

Multiple choice preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

An organic halide ,${C _2}{H _4}C{l _2}$ gives an unsaturated hydrocarbon on treatment with aloc .KOH,but ethanal on reaction with aq. KOH, the halide is:

  1. $C{H _3}CHC{l _2}$
  2. $C{H _2}ClC{H _2}Cl$

  3. a mixture of (a) and (b)

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Treatment with alcoholic KOH causes dehydrohalogenation to give an unsaturated hydrocarbon, while aqueous KOH substitutes halogens to form a carbonyl compound (ethanal). A geminal dihalide, specifically 1,1-dichloroethane (CH3CHCl2), yields ethanal upon hydrolysis with aqueous KOH.

Multiple choice preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

Preparation of alkylhalides by the reaction of alcohols and phosporous halide is _____ reaction.

  1. nucleophilic substitution

  2. electrophilic substitution

  3. addition

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

Preparation of alkylhalides by the reaction of alcohols and phosporous halide is nucleophilic substitution Reaction.
Becuase the nucleophile halide ion from phosporous halide like $PX _3,PX _5$  substitutes the $OH^{-}$ ion in alcohol, which is called as nucleophilic substitution reaction
e.g. $3CH _3-CH _2-OH+PCl _3\rightarrow 3C _2H _5-Cl+H _3PO _3$
Hence option A is correct.

Multiple choice preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

$C _2H _5OH+PCl _5\rightarrow $
In the above reaction which of the following alky halide is formed?

  1. $C _2H _5-Cl$
  2. $C _2H _5CH _2-Cl$
  3. $C _2H _5CH _2CH _2-Cl$

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$C _2H _5-Cl$ is the alkyl halide formed in the above reaction
$C _2H _5OH \ + \ PCl _5 \longrightarrow C _2H _5Cl \ + \ POCl _3 \ + \ HCl$
Hence option A is correct.