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 endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

Identify the following reactions as endothermic or exothermic.
(i) $2NaHCO _3+  {energy}\rightarrow Na _2CO _3+H _2O+CO _2$
(ii) $2Mg+O _2\rightarrow 2MgO+energy$

  1. (i) Exothermic (ii) Endothermic

  2. (i) Endothermic (ii) Exothermic

  3. (i) Exothermic (ii) Exothermic

  4. (i) Endothermic (ii) Endothermic
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Reaction with the absorption of energy is called an endothermic reaction.
In the reaction 

(i), Sodium Bicarbonate needs the energy to form sodium carbonate, water and carbon dioxide. 
Hence it is an endothermic reaction.
Reaction with the release of energy is called an exothermic reaction.
In the reaction 

(ii) on the burning of magnesium wire, magnesium oxide is formed by the release of energy in the form of heat and light.
Hence it is an exothermic reaction.

Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

Which of the following is not an endothermic reaction?

  1. $CaCO _3\rightarrow CaO+CO _2$
  2. $2H _2O\rightarrow 2H _2+O _2$
  3. $6CO _2+6H _2O\rightarrow C _6H _{12}O _6+6O _2$
  4. $C _6H _{12}O _6+6O _2\rightarrow 6CO _2+6H _2O$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$C _6H _{12}O _6+6O _2\rightarrow 6CO _2+6H _2O$  is not endothermic reaction.
It is a synthesis reaction . the reaction is called cellular respiration as it produces energy for the body to use for activity. n oxidizing the glucose, the cell takes the energy from this chemical process and uses it for ATP synthesis. The ATP synthase is considered to be the most important carrier of energy in a cell. It captures energy, then uses that energy to fuel other processes within the cell. While most are formed during respiration, some are also made during photosynthesis.
Heat is not absorbed so it is not an endothermic reaction

Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

The reaction between carbon and oxygen can be represented as:
$C(g)\ + \ O _2(g)\rightarrow CO _{2}(g) + heat$
In which of the following type(s), the above reaction can be classified?
I. Combustion reaction
II. Displacement reaction 
Ill. Endothermic reaction
IV. Combination reaction

  1. (I) and (III)

  2. (I), (III) and (IV)

  3. (I) and (IV)

  4. (I) only
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$C(g)+O _2(g)\rightarrow CO _2(g)+heat$

As, the carbon is combining with oxygen to form $CO _2$, it is a combination reaction and the oxidation of carbon is also taking place in the presence of oxygen, it is also a combustion reaction.

Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

When quickline is reacted with water, the reaction is:

  1. an endothermic reaction

  2. a reaction involving reduction

  3. an exothermic reaction

  4. a reaction involving oxidation
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Quicklime is reacted with water to form calcium hydroxide.

$CaO + H _2O\rightarrow Ca(OH) _2$
This reaction is exothermic reaction because some amount of heat evolved in the reaction.
So answer is C.

Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

$Si + C \rightarrow$ SiC. This chemical reaction is an example for:

  1. exothermic reaction

  2. endothermic reaction

  3. dissociation reaction

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

$Si + C \rightarrow SiC$.

This chemical reaction is an example of an exothermic reaction as heat is liberated during the reaction. It is also an example of a combination reaction. Two elements combine to form a single compound.

Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

Which of the following is/are endothermic reactions?

  1. $CaCO _{3}\rightarrow CaO+CO _{2}$
  2. $CH _{4}+2O _{2}\rightarrow CO _{2}+2H _{2}O$
  3. $2HgO\rightarrow 2Hg+O _{2}$
  4. $2H _{2}+O _{2}\rightarrow 2H _{2}O$
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Explanation
$CaCO _{3}\rightarrow CaO+CO _{2}$
is a decomposition reaction and requires energy for breaking bonds. Its an endothermic reaction.
$CH _{4}+2O _{2}\rightarrow CO _{2}+2H _{2}O$
Its a combustion reaction hence releases energy and is an exothermic reaction
$2HgO\rightarrow 2Hg+O _{2}$
is a decomposition reaction and requires energy for breaking bonds. Its an endothermic reaction.
$2H _{2}+O _{2}\rightarrow 2H _{2}O$
Its a combustion reaction hence releases energy and is an exothermic reaction
Thus A and D are endothermic reactions. Option A and D are correct
Multiple choice chemistry p- block elements-ii anomalous properties of nitrogen nitrogen - 15 group group 15 elements

$N _{2}H _{4}+2H _{2}O _{4}\rightarrow 4H _{2}O _2$. 


This equation suggests the use of $H _{2}O _{2}$ as :

  1. Bleaching agent

  2. Antisepics

  3. Restoring colour of old paintings

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

Hydrazine (N2H4) reacts with hydrogen peroxide as a rocket propellant, producing energy and gases for thrust. The equation suggests an oxidation reaction where H2O2 acts as an oxidizer. H2O2 is not used as bleaching agent, antiseptic, or for restoring paintings in this context.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

The products obtained on heating $LiNO _3$ will be?

  1. $LiNO _2+O _2$
  2. $Li _2O+NO _2+O _2$
  3. $Li _3N+O _2$
  4. $Li _2O+NO+O _2$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When LiNO3 is heated, it decomposes to Li2O, NO2, and O2. This is typical thermal decomposition of lithium nitrate. Option A gives nitrite, option C suggests nitride formation, and option D gives NO instead of NO2.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

$LiAlH 4$ is obtained by reacting an excess of ____  with an ethereal solution of $AlCl _3$:

  1. $LiCl$
  2. $LiH$
  3. $Li$
  4. $LiOH$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The reaction is ,


$4LiH + AlCl _3 \rightarrow LiAlH _4 + 3 LiCl$


by reacting $LiH$ in the presence of dry ether with $AlCl _3$ .

Multiple choice economics environment pollution international efforts for conserving biodiversity effects of pollution on environment government efforts in pollution control

Montreal Protocol was connected with

  1. Phasing out ODS

  2. Reduction in CFCs

  3. Replacing CFCs with Chlorine and Bromine

  4. All of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Montreal Protocol on substances that deplete the Ozone layer was signed in 1987 and was adopted in 1989 as a protocol to the Vienna convention. Till 2016, it sought to control HCFCs and CFCs. The Kigali amendment of 2016 added HFCs under the ambit of the Montreal Protocol. Initially, the protocol was designed to reduce the production of CFCs and Halons. Later 

CCl$ _{4}$, Trichloroethane and Methyl Bromide were included.
Hence, the correct answer is 'Reduction in CFCs.'

Multiple choice chemistry p- block elements-ii group 17 elements - general properties group 17 elements group 17 elements - properties

Which of the following statement is wrong? In the reaction $2KCl{ O } _{ 3 }+{ I } _{ 2 }\rightarrow 2KI{ O } _{ 3 }+{ Cl } _{ 2 }$?

  1. ${ Cl } _{ 2 }$ is more reactive than $I _{ 2 }$
  2. When $KCl{ O } _{ 3 }$ reacts with $I _{ 2 }$, ${ Cl } _{ 2 }$ is liberated
  3. $KCl{ O } _{ 3 }+{ I } _{ 2 }$ is a redox reaction and $I _{ 2 }$ is oxidized
  4. In the above reaction, $I _{ 2 }$ is reduced
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

the given reaction is

${ 2KClO } _{ 3 }+{ I } _{ 2 }\rightarrow { 2KIO } _{ 3 }+{ Cl } _{ 2 }$
in reactant,oxidation state of iodine in ${ I } _{ 2 }=0$
in product,oxidation state of iodine in${ IO } _{ 3 }^{ - }\quad $is 3
so,oxidation state of iodine change from 0 to5,so it is oxidlsed.

Multiple choice chemistry p- block elements-ii group 17 elements - general properties group 17 elements group 17 elements - properties

Addition of halogen $(C{l _2} or B{r _2})$ to alkenes goes through formation of :

  1. Carbocation

  2. Carbanion

  3. Cyclic halonium ion

  4. Carbon free radical
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The electrophilic addition of halogens to alkenes involves the formation of a cyclic halonium ion intermediate, which explains the anti-addition stereochemistry observed in these reactions.