Chemistry

Chemical Reactions and Equations

674 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 nature of matter heterogenous mixture - colloidal solution and its properties suspensions and colloids mixtures

Which reaction gives colloidal solution

  1. $2Cu+{Cl} _{2}\rightarrow {Cu} _{2}{Cl} _{2}$
  2. $2H{NO} _{3}+3{H} _{2}S\rightarrow 3S+4{H} _{2}O+2NO$
  3. $2Mg+{CO} _{2}\rightarrow 2MgO+C$
  4. $2Cu+{O} _{2}\rightarrow 2CuO$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The reaction 2HNO3 + 3H2S -> 3S + 4H2O + 2NO produces colloidal sulfur (S) in water, which is a classic example of preparing a colloidal solution via chemical reaction.

Multiple choice chemistry nature of matter heterogenous mixture - colloidal solution and its properties suspensions and colloids mixtures

Out of the following, which reaction gives a colloidal solution?

  1. $Cu + HgCl _{2}\rightarrow CuCl _{2} + Hg$
  2. $2HNO _{3} + 3H _{2}S\rightarrow 3S + 4H _{2}O + 2NO$
  3. $2Mg + CO _{2} \rightarrow 2MgO + C$
  4. $Cu + CuCl _{2}\xrightarrow {\text {in presence of excess of HCl}} Cu _{2}Cl _{2}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Similar to the previous question, the reaction of hydrogen sulfide with nitric acid produces sulfur, which forms a colloidal sol.

Multiple choice chemistry substances in common use chemical from common salt compounds of carbon some useful compounds in everyday life

Which one of the following processes does not occur during formation of $CH{ Cl } _{ 3 }$ from ${ C H } _{ 3 }OH$ and bleaching powder ?

  1. Hydrolysis

  2. Oxidation

  3. Reduction

  4. Chlorination
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
The process that does not occur during the formation of $CHCl _3$ from $CH _3OH$ and Bleaching Powder is REDUCTION PROCESS.
In $CHCl _3$ oxidation state of carbon is +2 and in methanol oxidation state of carbon is-2. This is reduction.
Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

Which of the following is the most exothermic reaction?

  1. $\displaystyle { Ag }^{ + }\left( aq \right) +{ Cl }^{ - }\rightarrow AgCl(aq) $
  2. $\displaystyle { C } _{ 5 }{ H } _{ 12 }\left( s \right) +8{ O } _{ 2 }\left( g \right) \rightarrow 5{ CO } _{ 2 }\left( g \right) +6{ H } _{ 2 }O\left( l \right) $
  3. $\displaystyle { NH } _{ 3 }\left( s \right) +{ H } _{ 2 }O\left( s \right) \leftrightharpoons { NH } _{ 4 }^{ + }\left( s \right) +{ OH }^{ - }\left( s \right) $
  4. $\displaystyle H{ C } _{ 2 }{ H } _{ 3 }{ O } _{ 2 }\left( l \right) +{ OH }^{ - }\left( aq \right) \rightarrow { H } _{ 2 }O\left( O \right) +{ C } _{ 2 }{ H } _{ 3 }{ O } _{ 2 }^{ - }\left( aq \right) $
  5. $\displaystyle Ca{ CO } _{ 3 }\left( s \right) \rightarrow CaO\left( s \right) +C{ O } _{ 2 }\left( g \right) $
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Option B is the correct answer.

The reaction written in option B is a combustion reaction. It is combustion of Propane. Combustion reactions are exothermic in nature.
Thus, combustion of propane is an exothermic reaction and a lot of heat is generated, which causes more propane to combine with Oxygen.

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 $AlCl _3$ .