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 chemistry carbon compounds some important carbon compounds ethanol and ethanoic acid introduction to alcohols - ethanol

Which of the following represents saponification reaction?

  1. $CH _{3}COONa + NaOH \xrightarrow{CaO} CH _{4} + Na _{2}CO _{3}$
  2. $CH _{3}COOH + C _{2}H _{5}OH \xrightarrow{H _{2}SO _{4}} CH _{3} COOC _{2}H _{5} +H _{2}O$
  3. $2CH _{3}COOH + 2Na \rightarrow 2CH _{3} COONa + H _{2}$
  4. $CH _{3}COOC _{2}H _{5} + NaOH \rightarrow CH _{3} COONa + C _{2} H _{5}OH$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Saponification is the alkaline hydrolysis of esters to form soap and alcohol. Therefore, the correct answer is option D.

$CH _{3}COOC _{2}H _{5} + NaOH \rightarrow CH _{3}COONa + C _{2}H _{5}OH$
    Ester                         Alkali                Soap               Alcohol

Multiple choice chemistry carbon compounds some important carbon compounds ethanol and ethanoic acid introduction to alcohols - ethanol

Explain the given reactions with the examples.
Oxidation reaction :

  1. ${ C } _{ 2 }{ H } _{ 5 }OH\xrightarrow { Alk.KMn{ O } _{ 4 } } { C }{ H } _{ 2 }OH{ COOH }$
  2. ${ C } _{ 2 }{ H } _{ 5 }OH\xrightarrow { Alk.KMn{ O } _{ 4 } } { C }{ H } _{ 3 }{ CH _3 }$
  3. ${ C } _{ 2 }{ H } _{ 5 }OH\xrightarrow { Alk.KMn{ O } _{ 4 } } { C }{ H } _{ 3 }{ CH _2OH }$
  4. ${ C } _{ 2 }{ H } _{ 5 }OH\xrightarrow { Alk.KMn{ O } _{ 4 } } { C }{ H } _{ 3 }{ COOH }$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Ethanol is oxidised to ethanoic acid in the presence of alkaline
$KMnO _{4}$ on heating
$CH _{3}  CH _{2}  OH \xrightarrow[Heat]{Alk.  KMnO _{4}} CH _{3}COOH$

Multiple choice chemistry hydrocarbons introduction to alkenes - ethyne acetylene alkynes

A hydrocarbon of molecular formula , ${C _6}{H _{10}}$ reacts with sodamide and the same on ozonolysis followed by hydrogen peroxide gives two molecules of carboxylic acids, one being optically active. Then the hydrocarbon may be

  1. $1$ hexyne
  2. $2- hexyne$
  3. $3$ hexyne
  4. $3$ methyl $1$ pentyne
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice chemistry hydrocarbons introduction to alkenes - ethyne acetylene alkynes

$C _{2}H _{2}$ on reaction with Na followed by reaction with $C _{2}H _{5}I$ gives 'X'. The molecular formula of 'X' is:

  1. $C _{2}H _{6}$
  2. $C _{4}H _{8}$
  3. $C _{4}H _{6}$
  4. $C _{3}H _{6}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Reaction: $CH \equiv CH \xrightarrow{Na} Na - C \equiv  CH \xrightarrow{C _2H _5I} C _2H _5 - C \equiv  CH + NaI$


Hence, the correct option is $C$

Multiple choice chemistry hydrocarbons introduction to alkenes - ethyne acetylene alkynes

1, 1, 2, 2-Tetra bromoethane $\xrightarrow {Zn}A$ $\xrightarrow{red hot \ tube}B$,


 Then B is:

  1. Acetylene

  2. Ethylene

  3. Ethane

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

$H-\overset{Br}{\overset{|}{\underset{Br}{\underset{|}{C}}}}-\overset{Br}{\overset{|}{\underset{Br}{\underset{|}{C}}}}-H\xrightarrow[\triangle]{2n}H-C\underset{(A)}{\equiv} C-H\xrightarrow{ red hot \ tube} C _6H _6$


Option D is correct.

Multiple choice chemistry hydrocarbons introduction to alkenes - ethyne acetylene alkynes

Which of the following reaction will give acetylene as a major product?

  1. $2[CH _{3}] \underset {\triangle}{\xrightarrow {Ag}}$
  2. $H _{3}C - CH _{2} - Br\underset {KOH}{\xrightarrow {alc.}}$
  3. $\underset {\underset {Br}{|}}{CH _{2}} - \underset {\underset {Br}{|}}{CH _{2}} \underset {\triangle}{\xrightarrow {Zn}}$

  4. All of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Only $2[CH _3] \xrightarrow[\Delta]{Ag} HC \equiv CH$ give acetylene

$B)$ $H _3C - CH _2 - Br \xrightarrow[KOH]{ak} CH _2 = CH _2$
$C)$ $\underset{Br}{\underset{|}{CH _2}} - \underset{Br}{\underset{|}{CH _2}} \rightarrow H _2C = CH _2$

Multiple choice chemistry hydrocarbons introduction to alkenes - ethyne acetylene alkynes

Ethene is obtained by dehydrobromination of:

  1. CHBr = CHBr
  2. $CH _3CHBr _2$
  3. $CH _3 - CH _2Br$

  4. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Dehydrobromination is an organic reaction in which alkyl halide when boiled with alc.alkali gives corresponding alkene called as beta-elimination reaction.

Multiple choice distinction between pairs of amines organic compounds containing nitrogen organic compounds with functional group containing nitrogen chemistry

Nitration of acetanilide followed by hydrolysis gives

  1. Ortho nitro aniline

  2. Para nitroaniline

  3. Ortho and para nitroaniline

  4. Ortho nitro anilinium ion
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Acetanilide is nitrated to form p-nitroacetanilide because the acetamido group is bulky, directing substitution to the para position. Subsequent hydrolysis of the amide group yields para-nitroaniline.

Multiple choice distinction between pairs of amines organic compounds containing nitrogen organic compounds with functional group containing nitrogen chemistry

p-chloroaniline and anilinium hydrochloride can be distinguished by :

  1. $Sandmeyer $ $reaction$
  2. $\displaystyle NaHCO _{3}$
  3. $\displaystyle AgNO _{3}$
  4. $carbylamines$ $ test$
Reveal answer Fill a bubble to check yourself
B,C Correct answer
Explanation

p-chloroaniline and anilinium hydrochloride can be distinguished by by using $AgNO _3$ and $NaHCO _3$, With $AgNO _3 $ anilinium hydrochloride gives white precipitate of $AgCl$. 


$NaHCO _3$ is a weak acid  which solublize anilinium hydrochloride and $CO _2$ gas liberates but  p-chloroaniline do not react with them.

Multiple choice distinction between pairs of amines organic compounds containing nitrogen organic compounds with functional group containing nitrogen chemistry

A compound $(X)$ with molecular formula $C _3H _9N$ react with $C _6H _5SO _2Cl$ to give a solid which is insoluble in alkali. $(X)$ is:

  1. $CH _3CH _2CH _2NH _2$
  2. $CH _3 - {\underset{CH _3}{\underset{|}{\overset{CH _3}{\overset{|}{N:}}}}}$
  3. $CH _3 - NH - CH _2CH _3$
  4. $CH _3 - {\underset{CH _3}{\underset{|}{CH}}} - NH _2$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Since the compound reacts with benzenesulphonyl chloride to give a product which is insoluble in alkali, it shows there is no $H$ attached to $N$ in the product . Hence, the compound $X$ is a secondary amine.
$CH _3 - NH - C-2H _5 + C _6H _5SO _2Cl \rightarrow \underset{N - Ethyl - N - methylbenzene sulphonamide}{CH _3 - {\underset{C _2H _5}{\underset{|}{N}}} - SO _2C _6H _5}$

Multiple choice distinction between pairs of amines organic compounds containing nitrogen organic compounds with functional group containing nitrogen chemistry

During preparation of arene diazonium salts, the excess of nitrous acid, if any, is destroyed by adding?

  1. $aq. \, NaOH$
  2. $aq. \, Na _2CO _3$
  3. $aq. \, NH _2CONH _2$
  4. $aq. \, KI$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Urea decomposes $HNO _2$ to give $N _2, \, CO _2 $ and $ H _2O$
$NH _2CONH _2+\, 2HONO \rightarrow 2N _2 \uparrow + \, CO _2 \uparrow +\, 3H _2O$

Multiple choice chemistry measurement and data processing and analysis spectroscopic identification of organic compounds materials science introduction superconducting metals and x-ray crystallography

Which of the following is not a nucleophile :

  1. $CH _3O^-$
  2. $H _2O$
  3. $CH _3-OCH _3$
  4. $CH _3-\underset{H}{\underset{|}{\overset{+}{O}}} - H$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Nucleophile are electron rich species, can donate their electron SO, $CH _3-\underset{H}{\underset{|}{\overset{+}{O}}} - H$ is not a Nucleophile.

Multiple choice chemistry derivatives of hydrocarbons alcohol nomenclature of alcohols and phenols introduction to alcohols

Identify 'C' in the following reaction. 


$C _2H _5Br       \overset{KCN}  {\longrightarrow} A \overset{H^+ H _2O}   {\longrightarrow} B \overset{LiAlH _4}{\longrightarrow} C$

  1. $Propan - 1 - ol$
  2. $Propanone$
  3. $2 - Ethyl - 3 - pentanone$
  4. $Propanal$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

C2H5Br + KCN -> C2H5CN (Propanenitrile). Hydrolysis -> C2H5COOH (Propanoic acid). Reduction with LiAlH4 -> C2H5CH2OH (Propan-1-ol).

Multiple choice chemistry combustion extinguishing fire ways to control fire combustion, fuels and flame

When water is poured over burning wood, the fire goes off. This is because _________.

  1. temperature of wood decreases

  2. temperature of water goes up

  3. molecules of water reacts with oxygen present in the flame

  4. the flame vapourises
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Water, when poured over fire absorbs large amount of heat and hence the temperature of wood falls below the ignition temperature. Thus the fire goes off.