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 enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

Which one of the following reactions is an example of auto-catalysis ?

  1. $2{ AsH } _{ 3 }(s)\rightarrow 2As(s)+3{ H } _{ 2 }(g)$
  2. ${ N } _{ 2 }(g)\rightarrow 3{ H } _{ 2 }(g)\overset { Fe(g) }{ \rightarrow } 2N{ H } _{ 3 }(g)$
  3. ${ 2SO } _{ 2 }(g)\rightarrow { O } _{ 2 }(g)\overset { NO(g) }{ \rightarrow } 2S{ O } _{ 3 }(g)$
  4. ${ C } _{ 12 }{ H } _{ 22 }{ O } _{ H }(l)+{ H } _{ 2 }O(l)\overset { { H }^{ - }(l) }{ \rightarrow } { C } _{ 6 }{ H } _{ 12 }{ O } _{ 6 }(l){ HC } _{ 6 }{ H } _{ 12 }{ O } _{ 6 }(l)$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Auto-catalysis is defined as the reaction that is catalyzed by one of its product.  in auto-catalysis product of reaction acts as a catalyst for the reaction.  In auto-catalysis the initial rate of reaction rises as the catalytic product is formed instead of decreasing steadily.  

for example: the free arsenic produced by decomposition of arsine auto catalyses the reaction. The thermal decomposition of Arsine produces arsenic and hydrogen.  2AsH3 forms 2As + 3H2

Multiple choice enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

In the reaction, $2KClO _3+MnO _2+2KCl+3O _2(g)+MnO _2$, which substance acts as catalyst?

  1. $O _2$
  2. $KClO _3$
  3. $MnO _2$

  4. KCl
  5. $O _2$ in the $MnO _2$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The catalyst used for the decomposition of potassium chlorate to oxygen is manganese dioxide $\displaystyle  MnO _2$.
In the reaction $\displaystyle 2KClO _3+MnO _2 \rightarrow 2KCl+3O _2(g)+MnO _2 $, we see that $\displaystyle  MnO _2$ is present on the reactant side as well as on the product side. Hence, it is a catalyst. We can rewrite the same reaction as: $\displaystyle 2KClO _3  \xrightarrow {MnO _2} 2KCl+3O _2(g)$. 

Multiple choice enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

In the reaction, $KMnO _4 + H _2SO _4 + H _2C _2O _4\xrightarrow{Mn^{2+}}$ Products, $Mn^{2+}$ ions act as:

  1. positive catalyst

  2. negative catalyst

  3. autocatalyst

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

Purple permanganate ions are reduced in acidic solution by oxalate ions to the nearly colorless manganese(II) ions, whereas the oxalate ions are oxidized to gaseous carbon dioxide: Obviously, the $Mn^{2+}$  ions act as catalyst. The reaction rate increases gradually even when no $Mn^{2+}$ ions are added because they are formed during the reaction meaning this product autocalyzes its own formation. 

Multiple choice enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

An example of an autocatalytic reaction is: 

  1. hydrogenation of oils

  2. decomposition of nitroglycerine
  3. oxidation of $Na _3AsO _3$ in presence of $Na _2SO _3$
  4. thermal decomposition of $KClO _3$ in presence of $MnO _2$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Reaction mechanism for the decomposition of nitroglycerine $4C _3H _5N _3O _9 \rightarrow 6N _2 + 12CO _2 + 10H _20 + O _2$.
This reaction is auto catalytic which is based upon internal redox chemistry.

Multiple choice enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

In the titration between oxalic acid and acidified potassium permanganate, the manganous salt formed during the reaction and catalyses the reaction. The manganous salt acts as: 

  1. promoter

  2. positive catalyst

  3. autocatalyst

  4. none of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In the tit-ration between oxalic acid and acidified potassium permanganate, the manganous salt formed during the reaction and catalyses the reaction. The manganous salt acts as auto catalyst because the rate of reaction depends on the manganous ions formed,so manganous ions catlyze the reaction.
Hence option C is correct.

Multiple choice chemistry nitrogen and sulfur nitrogen gas component of air - nitrogen nitrogen

$Ca+C _{2}\rightarrow CaC _{2} + N _2\rightarrow A$


Compound (A) is used as a/an:

  1. fertillizer

  2. dehydrating agent

  3. oxidising agent

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

$Ca+C _2\rightarrow CaC _2+N _2\rightarrow  Ca(CN) _2$


So, $CaC _2$ is used as ripening agent and $Ca(CN) _2$ used as fertilizer.


Hence, option A is correct.

Multiple choice chemistry nitrogen and sulfur nitrogen gas component of air - nitrogen nitrogen

Write the equation for the formation of ammonia by the action of water on magnesium nitride.

  1. $2{ Mg } _{ 3 }{ N } _{ 2 }+{ 6H } _{ 2 }O\rightarrow { 2NH } _{ 3 }+6Mg\left( OH \right) _{ 2 }$
  2. ${ Mg } _{ 3 }{ N } _{ 2 }+{ 3H } _{ 2 }O\rightarrow { NH } _{ 3 }+3Mg\left( OH \right) _{ 2 }$
  3. $3{ Mg } _{ 3 }{ N } _{ 2 }+{ 6H } _{ 2 }O\rightarrow { 6NH } _{ 3 }+3Mg\left( OH \right) _{ 2 }$
  4. ${ Mg } _{ 3 }{ N } _{ 2 }+{ 6H } _{ 2 }O\rightarrow { 2NH } _{ 3 }+3Mg\left( OH \right) _{ 2 }$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

${ Mg } _{ 3 }{ N } _{ 2 }+{ 6H } _{ 2 }O\rightarrow { 2NH } _{ 3 }+3Mg\left( OH \right) _{ 2 }$

Multiple choice chemistry nitrogen and sulfur nitrogen gas component of air - nitrogen nitrogen

The following reactions are carried out: 

$A:$ Nitrogen + metal $\rightarrow$ compound $X$
$B:$ $X$ + water $\rightarrow$ ammonia + another compound 
$C:$ Ammonia + metal oxide $\rightarrow$ metal + water + $N _2$

One metal that can be used for reaction $A$ is magnesium. Write the correctly balanced equation for reaction $B$, where $X$ is the compound formed.

  1. ${Na }{ N } _{ 2 }+{ H } _{ 2 }O\rightarrow { NH } _{ 3 }+Na _2O$
  2. ${Mg } _{ 3 }{ N } _{ 2 }+{ 3H } _{ 2 }O\rightarrow { 2NH } _{ 3 }+ 3MgO$
  3. ${Ca } _{ 3 }{ N } _{ 2 }+{ H } _{ 2 }O\rightarrow { NH } _{ 3 }+CaO$

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

One metal that can be used for reaction A is magnesium. So the corresponding reaction A is $N _2 + 3Mg\rightarrow Mg _3N _2$

Hence the compound X is $-\ Mg _3N _2$.
 

The complete reactions involving $Mg$ are as follows:

A: $N _2 + 3Mg\rightarrow Mg _3N _2$

B: $Mg _3N _2+6H _2O\rightarrow 3Mg(OH) _2+2NH _3$ 

C: $2NH _3+ 3MgO\rightarrow 3Mg+3H _2O+N _2$

The correct balanced equation for reaction B is $Mg _3N _2+6H _2O\rightarrow 3Mg(OH) _2+2NH _3$ 

Multiple choice zoology ecosystems decomposition in ecosystem ecosystem productivity and decomposition producers, consumers and decomposers

End product of 'aerobic' decomposition are:

  1. Unstable

  2. stable

  3. reactive

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

Aerobic decomposition results in stable end products like carbon dioxide, water, and nitrates, which are not prone to further rapid decay. Unstable products are typically associated with incomplete or anaerobic processes.

Multiple choice oxoacids of halogens p- block elements-ii p-block elements the p-block elements chemistry

Mixture of $KBr$ and $KBrO _3$ in acidic medium can be used as brominating agent.

The chemical reaction is, $ 5Br^{-} + xBrO^{-} _3 + 6H^{+} \rightarrow 3Br _y + 3H _2O$

Then $ x+y$ is :

  1. 6

  2. 3

  3. 5

  4. 11
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Reaction of process:

$ 5Br^{-} + BrO _3^{-} + 6H^{+} \rightarrow 3Br _2 + 3H _2O$
      -1               +5                               0

$x$ = 1 ,$y$ = 2

$x +y$ = 3

Here, bromide ion oxidises and $BrO _3^-$ reduces and bromine forms as a product.