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 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
B Correct answer
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.

Multiple choice preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

In the given reaction, identify the compound A.
$3C _2H _5OH+PBr _3\rightarrow A+H _3PO _3$.

  1. $C _2H _5Br$
  2. $CH _3C _2H _5Br$
  3. $CH _2CH _2CH _2CH _2-Cl$

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

A is $C _2H _5Br$
$3CH _3-CH _2-OH+PBr _3\rightarrow 3C _2H _5-Br+H _3PO _3$

Multiple choice preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

In the following reaction, identify the compound A.
$3CH _3-CH _2-OH+PCl _3\rightarrow 3C _2H _5-Cl+A$ .

  1. $H _3PO _2$
  2. $H _3PO _3$
  3. $H _3PO _4$
  4. $POCl _3$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A is $H _3PO _3$
$3CH _3-CH _2-OH+PCl _3\rightarrow 3C _2H _5-Cl+H _3PO _3$
Hence option A is correct.

Multiple choice preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

Which of the following is the byproduct when $R-OH$ is reacted with $PCl _3$?

  1. $POCl _3$
  2. $H _3PO _3$
  3. $HCl$

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


$H _3PO _3$ is the byproduct when R-Cl is reacted with $PCl _3$

$3R-OH+PCl _3\rightarrow R-Cl+ H _3PO _3$

In the final product, we get a byproduct of $H _3PO _3$

Hence option B is correct.
Multiple choice preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

In the given reaction, the product formed A and B are :
$3CH _3-CH _2-OH+PCl _3\rightarrow A+B$

  1. $3C _2H _5-Cl+H _2O$
  2. $3C _2H _5-Cl+HCl$
  3. $3C _2H _5-Cl+H _3PO _3$
  4. $3C _2H _5-Cl+POCl _3$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The products formed are $3C _2H _5-Cl+H _3PO _3$ when $3CH _3-CH _2-OH$ is reacted with $PCl _3$.


$3CH _3-CH _2-OH+PCl _3\rightarrow 3C _2H _5-Cl+H _3PO _3$
Hence option C is correct.



Multiple choice preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

In the following reaction which of the following are byproducts?
$C _2H _5OH+PCl _5\rightarrow $

  1. $POCl _3, HCl$
  2. $POCl _2, HCl$
  3. $PCl _3, HCl$

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

When ethanol reacts with phosphorous pentachloride, we get ethyl chloride as the main product whereas, phosphorous oxychloride and HCl as the byproducts.

Multiple choice preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

In the following reaction, identify the compound A.
$3CH _3-CH _2-OH+A\rightarrow 3C _2H _5-Cl+H _3PO _3$.

  1. $PCl _3$
  2. $PCl _5$
  3. $POCl _3$
  4. $H _2PO _2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A is $PCl _3$ in the above reaction.
$3CH _3-CH _2-OH+PCl _3\rightarrow 3C _2H _5-Cl+H _3PO _3$
Hence option A is corrcet.

Multiple choice preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

What is the product formed when $CH _3CH _2CH _2CH _2-OH$ is reacted with $PCl _3$ in presence of trimethyl amine?

  1. $CH _3CH _2CH _2CH _2-Cl$
  2. $CH _3CH(CH _3)CH _2CH _2-Cl$
  3. $CH _3CH _2C(CH _3) _2CH _2-Cl$
  4. $CH _3CH _2CH _2CH _2CH _2CH _2-Cl$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When Alcohol reacts with $PCl _{3}$ in presence of Trimethyl Amine. It is a nucleophile substitution halogenation reaction replaces $OH^{-}$  with $Cl^{-}$  

   $CH _{3}CH _{2}CH _{2}CH _{2} - OH\overset{PCl _{3}}{\rightarrow} CH _{3}CH _{2}CH _{2}CH _{2} - Cl $

Multiple choice preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

$3C _2H _5OH+A\rightarrow C _2H _5Br+H _3PO _3$.Which of the following is A ?

  1. $PBr _3$
  2. $PBr _5$
  3. $POBr _3$

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

The reagent used in the above reaction is $PBr _3$
$3CH _3-CH _2-OH+PBr _3\rightarrow 3C _2H _5-Cl+H _3PO _3$
Hence option A is correct.

Multiple choice preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

$CH _3CH _2C(CH _3) _2CH _2-OH+PCl _3\rightarrow A+H _3PO _4$. In the above reaction which of the following is A?

  1. $CH _3CH _2C(CH _3) _2CH _2-Cl$
  2. $CH _3CH _2CH(CH _3)CH _2-Cl$
  3. $CH _3CH _2CH _2CH _2-Cl$
  4. $CH _3CH(CH _3)C(CH _3) _2CH _2-Cl$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$CH _3CH _2C(CH _3) _2CH _2-OH+PCl _3\rightarrow CH _3CH _2C(CH _3) _2CH _2-Cl+H _3PO _4$
So in the above reaction A is $CH _3CH _2C(CH _3) _2CH _2-Cl$
Hence option A is correct.

Multiple choice preparation of haloalkanes halogen derivatives carbon tetrachloride ddt
Consider the following reaction:
$R-OH+PX _5\rightarrow R-X+B+HX$ 
What is B?
  1. $HPOX _3$
  2. $H _3PO _2$
  3. $H _3PO _3$
  4. $POX _3$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

B is $ \displaystyle POX _3$.
For example, when ethyl alcohol is refluxed with $ \displaystyle PCl _5$, ethyl chloride, HCl and phosphorous oxy chloride is obtained.
$ \displaystyle CH _3-CH _2-OH +PCl _5 \to CH _3-CH _2-Cl+POCl _3+HCl$