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 p- block elements-i study of aluminium chloride study of aluminium structure of some compounds

Substance which readily undergo hydrolysis are :

  1. $AlCl _3$
  2. $BCl _3$
  3. $SiCl _4$
  4. $PbCl _4$
Reveal answer Fill a bubble to check yourself
A,B,C,D Correct answer
Explanation
All the given compounds readily undergo hydrolysis.
$B{ Cl } _{ 3 }+3{ H } _{ 2 }O\longrightarrow B{ \left( OH \right)  } _{ 3 }+3HCl$
$Al{ Cl } _{ 3 }+3{ H } _{ 2 }O\longrightarrow Al{ \left( OH \right)  } _{ 3 }+3HCl$
$Si{ Cl } _{ 4 }+2{ H } _{ 2 }O\longrightarrow Si{ O } _{ 2 }+4HCl$
$Pb{ Cl } _{ 4 }+2{ H } _{ 2 }O\longrightarrow Pb{ O } _{ 2 }+4HCl$
Multiple choice chemistry environmental chemistry biochemistry and the environment green chemistry strategies to control environmental pollution and green chemistry

Which one of the following is not an application of green chemistry?

  1. Replacement of CFCs by ${CO} _{2}$ as lowing agent in the manufacture of polystyrene foam sheets

  2. Reacting methylamine and phsogene to produce metyl isocyanate

  3. Replacement of organotions by sea-nine as anti fouling compound in sea marines

  4. Catalytic dehydrogenation of the diethanol amine withou using cyanide and formaldehyde
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Green chemistry aims to reduce hazardous substances. Reacting methylamine and phosgene to produce methyl isocyanate is the process famously associated with the Bhopal disaster; it is highly toxic and definitely not an application of green chemistry.

Multiple choice zoology respiratory system do plants breathe? plant respiration respiration-plants

Free radicals are formed through

  1. Oxidation

  2. Reduction

  3. Hydrolysis

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

A.Oxidation – Release of electrons and protons or reaction with oxygen

B.Reduction – Acceptance of electrons and protons or release of oxygen.

C. Hydrolysis – Breaking of molecules in presence of water.

D.Synthesis – Process of formation of biomolecules.

So, the correct option is ‘oxidation’.

Multiple choice chemistry introduction to acid and base neutralisations in everyday life acids and bases in daily life neutralisation reaction

$X+H _2O\rightarrow Y$. 

$Y$ is used to remove grease stains from woollen clothes. Identify $X$ and $Y$.

  1. $X=HCl, Y=NaOH$
  2. $X=NH _4OH, Y=NH _3$
  3. $X=NH _3, Y=NH _4OH$

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

Ammonia solution is good for removing stains and tarnish and can also repel moths and reduce paint odours. As ammonia reacts with the water, it is dissolved in to produce ammonium ions and hydroxide ions.

Multiple choice chemistry polymer addition polymerisation types of polymerisation reactions petrochemicals and polymers

$\begin{bmatrix}-CH _2-\underset{\underset{\textstyle\;OH}{\displaystyle\mid}}{\;\;\;CH}-CH _2-\underset{\underset{\textstyle\;OH}{\displaystyle\mid}}{\;\;\;CH}-CH _2-\underset{\underset{\textstyle\;OH}{\displaystyle\mid}}{\;\;\;CH}-\end{bmatrix} _n$

Polyvinyl alcohol (as shown above) is a unique polymer having high affinity for water. Which of the following procedures would be most suitable for its preparation?

  1. radical chain polymerisation of $CH _2=CH-CH _2-OH$
  2. radical chain polymerisation of $CH _2=CH-OH$
  3. radical chain polymerisation of $CH _2=CH-CO _2CH _3$, following by base catalysed hydrolysis
  4. radical chain polymerisation of $CH _2=CH-OCOCH _3$, followed by acid catalysed hydrolysis
  5. radical chain polymerisation of $CH _2=CH-OCOCH _3$, followed by base catalysed hydrolysis
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$\begin{bmatrix}-CH _2-\underset{\underset{\textstyle\;OH}{\displaystyle\mid}}{\;\;\;CH}-CH _2-\underset{\underset{\textstyle\;OH}{\displaystyle\mid}}{\;\;\;CH}-CH _2-\underset{\underset{\textstyle\;OH}{\displaystyle\mid}}{\;\;\;CH}-\end{bmatrix} _n$ 


Polyvinyl alcohol is prepared by radical chain polymerisation of  $CH _2=CH-OCOCH _3$, followed by base catalysed hydrolysis in which acetate group is replaced by hydroxide group. 

Multiple choice chemistry petrochemicals and polymers addition polymerisation types of polymerisation reactions polymer

Order the following monomers with respect to their expected reactivity toward cationic polymerization and explain your answer.
$\displaystyle { H } _{ 2 }C={ CHCH } _{ 3 }$, $\displaystyle { H } _{ 2 }C=CHCl$, $\displaystyle { H } _{ 2 }C=CH-{ C } _{ 6 }{ H } _{ 5 }$, $\displaystyle { H } _{ 2 }C={ CHCO } _{ 2 }{ CH } _{ 3 }$.

  1. $\displaystyle { H } _{ 2 }C={ CHCO } _{ 2 }{ CH } _{ 3 }\quad <\quad { H } _{ 2 }C=CHCl\quad <\quad { H } _{ 2 }C{ =CHCH } _{ 3 }\quad <\quad { H } _{ 2 }C=CH\quad -{ C } _{ 6 }{ H } _{ 5 }$
  2. $\displaystyle { H } _{ 2 }C=CHCl\quad <{ H } _{ 2 }C={ CHCO } _{ 2 }{ CH } _{ 3 }\quad <\quad { H } _{ 2 }C{ =CHCH } _{ 3 }\quad <\quad { H } _{ 2 }C=CH\quad -{ C } _{ 6 }{ H } _{ 5 }$
  3. $\displaystyle { H } _{ 2 }C={ CHCO } _{ 2 }{ CH } _{ 3 }\quad <\quad { H } _{ 2 }C{ =CHCH } _{ 3 }\quad <\quad { H } _{ 2 }C=CHCl\quad <\quad { H } _{ 2 }C=CH\quad -{ C } _{ 6 }{ H } _{ 5 }$
  4. $\displaystyle { H } _{ 2 }C={ CHCO } _{ 2 }{ CH } _{ 3 }\quad <\quad { H } _{ 2 }C=CHCl\quad <\quad { H } _{ 2 }C=CH\quad -{ C } _{ 6 }{ H } _{ 5 } <\quad { H } _{ 2 }C{ =CHCH } _{ 3 }\quad$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$\text{reactivity is proportional to tendecy of donating electron by braking double bonds.}$

$\displaystyle { H } _{ 2 }C={ CHCO } _{ 2 }{ CH } _{ 3 }\quad <\quad { H } _{ 2 }C=CHCl\quad <\quad { H } _{ 2 }C{ =CHCH } _{ 3 }\quad <\quad { H } _{ 2 }C=CH\quad -{ C } _{ 6 }{ H } _{ 5 }$

Multiple choice chemistry petrochemicals and polymers addition polymerisation types of polymerisation reactions polymer

Which of the following alkenes is most reactive towards cationic polymerization?

  1. ${ CH } _{ 2 }$ = ${ CHCH } _{ 3 }$
  2. ${ CH } _{ 2 }$ = $CHCl$
  3. ${ CH } _{ 2 }$ = ${ CHC } _{ 6 }{ H } _{ 5 }$
  4. ${ CH } _{ 2 }$ = ${ CHCOOCH } _{ 3 }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In cationic polymerization the most stable cation will show the highest reactivity.

The order of reactivity will be-

$CH _2 = CH-C _6H _5 > CH _2  = CHCH _3 > CH _2 = CHCl >CH _2 = CHCOOCH _3$

Option C is correct.

Multiple choice chemistry air and water pollution control smoke, dust and other air pollutants, acid rain air pollutants and its effects air and air pollution

High concentration of NO are dangerous because it converts to 

  1. $N _2O$
  2. $NO _2$
  3. $N _2O _5$
  4. $N _2O _3$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
  1. When exposed to oxygen, ntric oxide is converted into nitrogen dioxide  $2NO+{ O } _{ 2 }→2N{ O } _{ 2 }$
  2.  Nitrogen dioxide , a brown toxic gas and a major air pollutant.
Multiple choice chemistry the p-block elements - group 13 study of orthoboric acid some important compounds of boron study of boron

$\displaystyle B(OH) _{3}+NaOH\rightleftharpoons NaBO _{2}+Na[B(OH) _{4}]+H _{2}O$ 

How can this reaction is made to proceed in forward direction?

  1. Addition of cis 1,2 diol

  2. Addition of borax

  3. Addition of trans 1,2 diol
  4. Addition of $Na _{2}HPO _{4}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

cis -1,2 diol is added to make the recation proceed in the forward direction.

Multiple choice chemistry the p-block elements - group 13 study of orthoboric acid some important compounds of boron study of boron

$H _{3}BO _{3}\xrightarrow{T _{1}}X \xrightarrow{T _{2}} Y\xrightarrow{red hot} B _{2}O _{3}$ if $T _{1}<T _{2}$then X and Y respectively are :

  1. X=Metaboric acid and Y= Tetraboric acid

  2. X=Tetraboric acid and Y= Metaboric acid

  3. X=Borax and Y= Metaboric acid

  4. X=Tetraboric acid and Y= Borax
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$H _{3}BO _{3}\xrightarrow{100^oC}HBO _2 \xrightarrow{160^oC} H _2B _4O _7\xrightarrow{red hot} B _{2}O _{3}$
X is $HBO _2$ which is metaboric acid and Y is $H _2B _4O _7$ which is tetraboric acid.

Multiple choice chemistry the p-block elements - group 13 study of orthoboric acid some important compounds of boron study of boron

$B(OH) _3+NaOH\rightarrow Na[B(OH) _4] _{(aq)}$

Then addition of which of the following proceeds the reaction in the forward direction :

  1. cis-1, 2 diol

  2. trans 1, 2 diol

  3. borax
  4. $Na _2HPO _4$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$B(OH) _3+NaOH\rightarrow Na[B(OH) _4] _{(aq)}$

This reaction is reversible reaction because sodium metaborate, $ Na [B(OH) _4]$ formed by the reaction between $B(OH) _3$ and NaOH gets hydrolysed to regenerate $B(OH) _3$ and NaOH.

$ Na [B(OH) _4]$ $\overset {hydrolysis}\rightarrow$ $NaOH$ + $B(OH) _3$

If, some quantity of polyhydroxy compounds like cis- 1, 2-diol, catechol, glycerol etc is added to the reaction mixture then the $B(OH) _3$ combines with such polyhydroxy compounds to give chelated complex compound. Due to complex compound formation, stability increases and due to higher stability of complex, reaction moves in forward direction.