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 group 17 elements - trends in chemical properties group 17 elements - properties p- block elements-ii p-block elements chemistry

Iodine is oxidised by fuming nitric acid. The major product formed is:

  1. $HI$
  2. $HIO _2$
  3. $HIO _3$
  4. $HIO _4$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Reaction of iodine with fuming nitric acid is given by 

${ I } _{ 2 }+{ 10HNO } _{ 3 }\longrightarrow { 2HIO } _{ 3 }+{ 10NO } _{ 2 }+{ 4H } _{ 2 }O$.
So, the major product formed will be ${ HIO } _{ 3 }$.
So, correct answer is option $C$.

Multiple choice group 17 elements - trends in chemical properties group 17 elements - properties p- block elements-ii p-block elements chemistry

Identify (a) and (b).

$ Br _2 + \underset {hot  }{ OH^- } \rightarrow (a) + (b) $

$ (a) + (b) + H^+ \rightarrow Br _2 $ :

  1. a- $Br^-$
  2. b- $BrO$
  3. a- $BrO$
  4. b- $BrO _3^-$

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

Method is for enriching $Br _2$:

$ 3Br _2 + 6 OH^{-} \rightarrow \underset {(A)  }{ 5Br^- }+ \underset {(B)  }{ BrO^- _3} $ +$3H _2O$

$ 5Br^- + BrO^- _3 + 6H^+ \rightarrow 3Br _2 + 3H _2O $

Hence,option A and D is correct.

Multiple choice chemistry production of metals extraction of metal from concentrated ore basics of metallurgy extraction of metals from ore

Which of the following is reactions is an example of autoreduction? 

  1. $Fe _3O _4+4CO\rightarrow 3Fe+4CO _2$
  2. $CuO+C\rightarrow 2Cu+CO$
  3. $Cu^{2+} _{(aq)}+Fe _{(s)}\rightarrow Cu _{(s)}+Fe^{(2+)} _{(aq)}$
  4. $Cu _2O+\frac{1}{2}Cu _2S\rightarrow 2Cu+\frac{1}{2}SO _2$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The sulphide ores of certain less electropositive metals like those of Hg, Pb, Cu, etc. when heated in air bring about the conversion of a part of the sulphide ore to oxide or sulphate which then reacts with the remaining sulphide to give the matal and $SO _2$. No external reducing agent is used in this process.
$2Cu _2S+3O _2\rightarrow 2Cu _2O+3SO _2$
$2Cu _2O+Cu _2S\rightarrow 6Cu+ SO _2$

Multiple choice chemistry production of metals extraction of metal from concentrated ore basics of metallurgy extraction of metals from ore

The above process is:

$HgS\xrightarrow{O _2}HgS.HgO$
                         $\downarrow\Delta$
                        $Hg$ 

  1. auto oxidation

  2. self reduction

  3. thermal reduction

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

Cinnabar ($HgS$), when heated with a current of $O _2$ gets reduced to $Hg$ without the need of any additional reducing agent. The process involved is known as self reduction

Multiple choice chemistry production of metals extraction of metal from concentrated ore basics of metallurgy extraction of metals from ore

Which of the following reduction processes are correct?

  1. ${Fe _2O _3+C\overset{Reduction}{\rightarrow}Fe}$
  2. ${ZnO+C\overset{Reduction}{\rightarrow}Zn}$
  3. ${SnO _2+C\overset{Reduction}{\rightarrow}Sn}$
  4. ${PbO+C\overset{Reduction}{\rightarrow}Pb}$
Reveal answer Fill a bubble to check yourself
A,B,C,D Correct answer
Explanation

Reduction is loss of oxygens.
In all the above reactions the metal oxides are reduced to metals by the elimination of oxygens,so all are reduction ractions.
Hence options A,B,C & D are correct.

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

$KClO _3$ on heating decomposes  into $KCl$ and $O _2$. If some $MnO _2$ is added, the reaction goes much faster because :

  1. $MnO _2$ decomposes to give oxygen
  2. $MnO _2$ provides heat by reacting
  3. better contact is provided by $MnO _2$
  4. $MnO _2$ acts as a catalyst
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The reaction is as follows:
$2KClO _3\xrightarrow {heat} 2KCl+3O _2$
In this reaction, if $MnO _2$ is used, then the reaction become faster due to catalytic activities of $MnO _2$.

(Catalyst is a substance which lowers activation energy of reaction because it provides alternate pathway for reaction. Also, it increases the rate of backward and forward reaction with same extent. Due to this lower activation energy, equilibrium is attained faster but it doesnot change the overall enthalpy of the reaction.)

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

Match the reaction of Column - I with the catalysts in Column - II:

Column - I(Reaction) Column - II(Catalyst)
(a) $2KClO _3(s) \rightarrow 2KCl(s) +3O _2(g)$ (p) $Al _2O _3$
(b) $ 2SO _2(g) +O _2(g) \rightarrow 2SO _3(g)$ (q) $Pt$
(c) $2H _2O _2(l) \rightarrow 2H _2O(l) +O _2(g)$ (r) $V _2O _5$
(d) $ N _2(g) + 3H _2 (g) \rightarrow 2NH _3 (g)$ (s) $MnO _2$
  1. $a\rightarrow s,b\rightarrow r,c\rightarrow s,d\rightarrow p\ \& \ q$
  2. $a\rightarrow p,b\rightarrow r,c\rightarrow s,d\rightarrow p\ \& \ s$
  3. $a\rightarrow q,b\rightarrow r,c\rightarrow s,d\rightarrow q$
  4. $a\rightarrow s,b\rightarrow r,c\rightarrow q,d\rightarrow p\ \& \ q$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

a)  For $KClO _3$ decomposition Manganeese(IV) oxide is used as catalyst at an elevated temparature of 150 degree given by the formula $MnO _2$.


b) The catalyst that promotes the $SO _2$ oxidation at temparature of 500 degree where $SO _2$ is thermodynamically efficient is vanadium pentoxide given by $V _2O _5$.


c) The catalyst that provides alternative way with low activation energy  for decomposition of $H _2O _2$ is $MnO _2$.

d) Synthesis of Ammonia by Haber process uses $Pt$ and $Al _2O _3$ as a compromise catalysts in place of $Fe$.

Option A is correctt.

Multiple choice chemistry energy rocks and minerals petroleum and natural gas fossil fuels

Octane number can be changed by :

  1. alkylation

  2. cyclisation

  3. isomerisation

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

All the three reactions, i.e. alkylation, cyclisation, and isomerisation convert straight-chain hydrocarbons to branched-chain or cyclic compounds, which changes the percentage of straight-chain hydrocarbon. 


Hence, the octane number is changed.

So, the correct option is D.

Multiple choice chemistry energy rocks and minerals petroleum and natural gas fossil fuels

Reforming (also called aromatization) is the conversion of aromatic hydrocarbons into aliphatic hydrocarbons containing the same number of carbon atoms.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Reforming (also called aromatization) is the conversion of aliphatic hydrocarbons into aromatic hydrocarbons containing the same number of carbon atoms.

Multiple choice chemistry energy rocks and minerals petroleum and natural gas fossil fuels

Most of the chemical reactions in Cracking is based on:

  1. Carbocation formation

  2. Carbanion formation

  3. Radical formation

  4. Zwitter ion formation
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In cracking, the initial process involves the breaking down of hydrocarbons into free radicals.Only a small fraction of the feed molecules actually undergo initiation, but these reactions are necessary to produce the free radicals that drive the rest of the reactions.

Multiple choice geography in the land of kerala introduction to metallurgy occurrence of metals study of kerala

Which of the following is NOT calcination?

  1. $Fe(OH) _3.xH _2O\rightarrow Fe _2O _3+H _2O$
  2. $CuCO _3.Cu(OH) _2\rightarrow^ 2CuO+CO _2+H _2O$
  3. $CaCO _3\rightarrow^ CaO+CO _2$
  4. $(NH _4) _2CO _3\rightarrow^ 2NH _3+CO _2+H _2O$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Calcination is a process of heating to high temperature in air or oxygen, however calcination is also used to mean a thermal treatment process in the absence or limited supply of air or oxygen.

$(NH _4) _2CO _3$ is not an ore.so, it do not undergo calcination.

Multiple choice chemistry chemical kinetics dependence of reaction rate on concentration of reactants order of reactions factors influencing rate of a reaction

The given reaction 
$2FeCl _{3}+SnCl _{2}\rightarrow 2FeCl _{2}+SnCl _{4}$
Is an example of:

  1. Third order reaction

  2. First order reaction

  3. Second order reaction

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

For the third order reaction, the general reaction can be written as,

$A+B+C\rightarrow Products\ r={ K } _{ 3 }\left[ A \right] ^{ 2 }\left[ B \right] ^{ 1 }$
$r=\left[ Fe{ Cl } _{ 2 } \right] ^{ 2 }\left[ Sn{ Cl } _{ 4 } \right] ^{ 1 }$
the order of products are third order.

Multiple choice chemistry chemical kinetics dependence of reaction rate on concentration of reactants order of reactions factors influencing rate of a reaction

The following mechanism has been proposed for the reaction of $NO$ with $\displaystyle Br _{2}$ to form $NOBr$


$NO(g)+Br _{2}(g)\rightleftharpoons NOBr _{2}(g)$
$NOBr _{2}(g)+NO(g)\rightarrow 2NOBr(g)$


If the second step is the rate determining step,the order of the reaction with respect to $NO(g)$ is:

  1. 2

  2. 1

  3. 0

  4. 3
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In the mechanism, the first step is a fast equilibrium: K = [NOBr2] / ([NO][Br2]). The second step is the rate-determining step: Rate = k2[NOBr2][NO]. Substituting the equilibrium expression: Rate = k2 * K * [NO][Br2] * [NO] = k' [NO]^2 [Br2]. The order with respect to NO is 2.

Multiple choice chemistry chemical kinetics dependence of reaction rate on concentration of reactants order of reactions factors influencing rate of a reaction

The reaction, $CH _3COOC _2H _5+NaOH\rightarrow CH _3COONa+C _2H _5OH$ is:

  1. bimolecular reaction

  2. second order reaction

  3. third order reaction

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

The reaction, $CH _3COOC _2H _5+NaOH\rightarrow CH _3COONa+C _2H _5OH$ is bimolecular and second order reaction,as it contains two diiferent types of molecules.
Rate = $ k$ [$CH _3COOC _2H _5$] [$NaOH$]

Multiple choice chemistry chemical kinetics dependence of reaction rate on concentration of reactants order of reactions factors influencing rate of a reaction

For the reaction: $2NO+Cl _2\rightarrow 2NOCl$, the following mechanism was proposed on the basis of experimental observation.
$NO+Cl _2\overset {Fast}{\rightleftharpoons}NOCl _2$
$NOCl _2+NO\xrightarrow {Slow}2NOBr$
The order of reaction is:

  1. 2nd order

  2. pseudo 2nd order

  3. 3rd order

  4. first order
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

From the slow step, the rate law for the reaction is rate $\displaystyle = k' [NOCl _2][NO]$.....(1)


 $\displaystyle NOCl _2$ is an intermediate and its concentration is obtained from fast step (equilibrium step)

 $\displaystyle [NOCl _2] = K[NO][Cl _2]$......(2)

Substitute (2) in (1)
 $\displaystyle rate = k'K [NO][Cl _2][NO]$

Hence, rate $\displaystyle = k [NO]^2[Cl]$

The reaction is of second order in NO and first order in $\displaystyle Cl _2$. The overall reaction order is  $\displaystyle 2 + 1 = 3$