Chemistry

Chemical Reactions and Processes

571 Questions

Chemical reactions and processes questions cover the transformation of substances through electrolysis, thermal decomposition, and catalysis. Key areas include identifying gas evolution, balancing chemical equations, and understanding industrial chemical applications. This general chemistry topic is a staple in the science sections of multiple competitive examinations.

Thermal decompositionElectrolysis processGas evolution reactionsHeterogeneous catalystsFuel cell components

Chemical Reactions and Processes Questions

Multiple choice applications of adsorption adsorption adsorption and colloids surface chemistry chemistry

Which of the following increase(s) the activation of a solid adsorbent?

  1. Polishing the surface of the solid adsorbent.

  2. Sub-dividing the solid adsorbent.

  3. Blowing superheated steam through the porous adsorbent.

  4. Adsorption at very low pressure.
Reveal answer Fill a bubble to check yourself
B,C Correct answer
Explanation

Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid, or dissolved solid to a surface.
Adsorption of gases on solids depends on the following factors:

1) Surface area of the adsorbent: Adsorption is surface phenomenon. The extent of adsorption is directly proportional to the surface area of adsorbent. Finely divided metals and porous solids like charcoal, silica gel etc. posses more surface area when compared with solid lumps. 

2) Effect of pressure: Extent of adsorption increases with an increase in equilibrium pressure.

3) Nature of the gas: Since physical adsorption is non-specific, every gas gets adsorbed on the surface of any solid. Under a given conditions of temperature and pressure, the easily liquefiable gases such as $NH _3, HCl$ and $SO _2$ are adsorbed more than the gases like $H _2, N _2$ and $CO$. The ease with which a gas can be liquefied is determined by its critical temperature, $T _c$. 

Polishing the surface of the solid adsorbent makes no effect on adsorption.

Multiple choice applications of adsorption adsorption adsorption and colloids surface chemistry chemistry

Which of the following is/are application(s) of adsorption?

  1. De-ionization of water

  2. Gas masks
  3. Hygroscopic nature of $CaCl _2$

  4. Heterogeneous catalysis
Reveal answer Fill a bubble to check yourself
A,B,D Correct answer
Explanation
Adsorption :
The phenomenon of attracting and retaining the molecules of a substance on the surface of a liquid or a solid resulting into a higher concentration of the molecules on the surface is called adsorption. As a result of adsorption, there is a decrease of surface energy. The process of removal of an adsorbed substance from the surface on which it is adsorbed is called desorption. It is the reverse of adsorption and can be brought about by heating or by reducing the pressure.

Adsorption finds extensive applications both in research laboratory and in industry. A few applications are discussed below:
In gas masks:
All gas masks are devices containing suitable adsorbent so that the poisonous gases present in the atmosphere are preferentially adsorbed and the air for breathing is purified.
In heterogeneous catalysis:
The action of certain solids as catalysts is best explained in terms of adsorption. The theory is called adsorption theory. According to this theory, the gaseous reactants are adsorbed on the surface of the solid catalyst. As a result, the concentration of the reactants increases on the surface and hence, the rate of reaction increases. The theory is also able to explain the greater efficiency of the catalyst in the finely divided state, the action of catalyst promoters and poisons.
In softening of hard water (De-ionization of water):
The use of ion exchangers for softening of hard water is based upon the principle of competing adsorption just as in chromatography. Hygroscopic nature of $CaCl _2$ is not related to adsorption.

Multiple choice applications of adsorption adsorption adsorption and colloids surface chemistry chemistry

Which of the following can adsorb largest volume of hydrogen gas?

  1. Finely divided platinum

  2. Finely divided nickel

  3. Colloidal solution of palladium

  4. Colloidal Hydroxide
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Colloidal solution of palladium can adsorb largest volume of hydrogen gas as the surface area of palladium is maximum in its colloidal solution. Higher is the surface area of catalyst, larger will be the volume of hydrogen adsorbed.

Multiple choice chemistry phenomena around us changes and its classification types of changes classification of changes

Examples of slow reaction are:

  1. rusting of iron

  2. weathering of rocks

  3. neutralization of sodium hydroxide by hydrochloric acid

  4. formation of coal
Reveal answer Fill a bubble to check yourself
A,B,D Correct answer
Explanation
Reactions that take a while are slow reactions and those which occur within a few seconds are fast reactions. The rusting of iron, the fermentation of sugar into alcohol, the chemical weathering of rocks (breaking down of rocks), the photosynthesis process in plants, coal formation are slow reactions. Whereas neutralization reaction of a strong base like sodium hydroxide and strong acid like $HCl$ is a fast reaction.
option A,B,D are correct
Multiple choice chemistry chemical reactions of organic compounds commercially important alcohols - methanol methanol some commercially important alcohols uses of alcohols

Methanol is never stored in aluminium vessel because:

  1. it reacts with aluminium forming toxic gas

  2. it results in explosion

  3. it corrodes the the metal by destroying its oxide layer

  4. aluminium reduces methanol to methane
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Aluminum and its alloys resist most alcohols, however, some alcohols like methanol can be very corrosive when  extremely dry, especially at elevated temperatures.

Multiple choice evs water: a precious resource importance of water let's play with water water and its properties water resources and conservation

What is the final product when oxygen and hydrogen are mixed in a test tube at room temperature?

  1. Hydrogen peroxide

  2. Water

  3. A base

  4. A zwitterion

  5. No reaction takes place
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

The gas-phase oxidation of hydrogen has been extensively studied over a wide range of temperatures and pressures.


$H _2 + \dfrac {1}{2} O _2 \rightarrow H _2O$ ,$ \Delta H^o= -242 kj/mol$
$H _2(g) + \dfrac {1}{2}O _2(g) \rightarrow H _2O(g) $        $\Delta H^o = –242 kJ/mol$

This reaction does not take place at all when the two gases are simply mixed at room temperature. 

At temperatures around 500-600°C it proceeds quite smoothly, but when heated above 700° or ignited with a spark, the mixture explodes.

Hence the correct option is E.


Multiple choice chemistry study of compounds a. hydrogen chloride laboratory method of preparation of hydrochloric acid physical and chemical properties and uses of hydrochloric acid hydrogen chloride: occurrence, preparation, purification and identification

Select the correct statement among the following.

  1. Hydrogen chloride is prepared by passing chlorine gas through hot water

  2. Hydrogen chloride is produced by combination of moist hydrogen gas with chlorine in the presence of diffused sunlight

  3. Hydrogen chloride can't be produced in the dark

  4. Activated carbon is used as a catalyst in the synthesis of hydrogen chloride
Reveal answer Fill a bubble to check yourself
B,D Correct answer
Explanation
Hydrogen chloride is produced by a combination of moist hydrogen gas with chlorine in the presence of diffused sunlight. The reaction should be maintained in diffused but not in direct sunlight as it is an explosive reaction. And not even in dark as it is very slow (negligible). Activated carbon is used as a catalyst in the synthesis of hydrogen chloride.
Hence, options $B$ and $D$ are correct.
Multiple choice chemistry study of compounds a. hydrogen chloride laboratory method of preparation of hydrochloric acid physical and chemical properties and uses of hydrochloric acid hydrogen chloride: occurrence, preparation, purification and identification

Moist hydrogen gas combines with chlorine in the presence of diffused sunlight to form $HCl$. The catalyst used here is :

  1. oxygen.

  2. silica.

  3. alum.

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

Moisture acts as a catalyst in the formation of HCl gas.


It acclerates the reaction.

It provides a reacting medium to hydrogen and chlorine gas.

It increases the interaction between them.


Hence, the correct option is $D$.


Multiple choice chemistry study of compounds a. hydrogen chloride laboratory method of preparation of hydrochloric acid physical and chemical properties and uses of hydrochloric acid hydrogen chloride: occurrence, preparation, purification and identification

In the laboratory preparation of $HCl$, which of the following are preferred?

  1. Conc. $H _2SO _4$ as reactant
  2. Conc. $H _2SO _4$ as drying agent
  3. Temperature of reaction mixture below $200^0C$

  4. Use of activated carbon as catalyst
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
Explanation

The laboratory preparation of $HCl$ includes dehydration of hydrochloric acid with sulphuric acid. It can also be generated by the reaction of sulphuric acid with sodium chloride. 


The reaction occurs at room temperature. Sulphuric acid acts as a reactant as well as a drying agent.

$NaCl+H _2SO _4 \rightarrow NaHSO _4+HCl$

Hence, the correct options are $\text{A}$, $\text{B}$ and $\text{C}$

Multiple choice chemistry study of compounds a. hydrogen chloride laboratory method of preparation of hydrochloric acid physical and chemical properties and uses of hydrochloric acid hydrogen chloride: occurrence, preparation, purification and identification

Metal chloride + Sulphuric acid$\longrightarrow$.............. + Hydrogen chloride :

  1. Metallic sulphate

  2. Metallic bisulphate

  3. Metallic sulphide

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

Metal chloride reaction with sulphuric acid is a double displacement reaction which form a metallic sulphate.

For example :-
$Na _2SO _4$ formed when $NaCl$ reacts with $H _2SO _4$ as

$\underset{chloride}{\underset{metal}{2NaCl}} + \underset{acid}{\underset{sulphuric}{H _2SO _4}} \xrightarrow{\Delta} \underset{Sulphate}{\underset{metallic}{Na _2SO _4}} + \underset{chloride}{\underset{Hydrogen}{2HCl}}$

Multiple choice chemistry study of compounds a. hydrogen chloride laboratory method of preparation of hydrochloric acid physical and chemical properties and uses of hydrochloric acid hydrogen chloride: occurrence, preparation, purification and identification

Identify the gas evolved when potassium sulphite is treated with dilute hydrochloric acid.

  1. ${ S } _{ 2 }$
  2. ${ O } _{ 2 }$
  3. ${ SO } _{ 2 }$

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

When potassium sulphite is treated with dilute hydrochloric acid, sulphur dioxide gas is evolved along with potassium chloride and water.


$ { K } _{ 2 }{ SO } _{ 3 }+HCl\rightarrow KCl + { H } _{ 2 }O+{ SO } _{ 2 }$

Hence, option C is correct.

Multiple choice chemistry study of compounds a. hydrogen chloride laboratory method of preparation of hydrochloric acid physical and chemical properties and uses of hydrochloric acid hydrogen chloride: occurrence, preparation, purification and identification

Which of the following gas is evolved when concentrated hydrochloric acid is made to react with manganese dioxide?

  1. ${ O} _{ 3 }$
  2. ${ O } _{ 2 }$
  3. ${ H} _{ 2 }$
  4. ${ Cl } _{ 2 }$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

When concentrated hydrochloric acid reacts with manganese dioxide, chlorine gas as well as manganese(II) chloride and water. 


${ MnO } _{ 2 }+4HCl\rightarrow { MnCl } _{ 2 }+{ Cl } _{ 2 }+2{ H } _{ 2 }O$

Hence, option $\text{D}$ is correct.

Multiple choice chemistry study of compounds a. hydrogen chloride laboratory method of preparation of hydrochloric acid physical and chemical properties and uses of hydrochloric acid hydrogen chloride: occurrence, preparation, purification and identification

Iron reacts with hydrogen chloride gas-forming (iron [II] chloride, iron [III] chloride) and hydrogen, The reaction is an example of :

  1. double decomposition

  2. synthesis

  3. simple displacement

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

Iron reacts with hydrogen chloride gas-forming iron$ [II] $ chloride and hydrogen. The reaction is an example of simple displacement reaction.


$Fe + 2HCl \longrightarrow FeCl _2 + H _2$


Hence, the correct answer is option $\text{D}$.

Multiple choice chemistry study of compounds a. hydrogen chloride laboratory method of preparation of hydrochloric acid physical and chemical properties and uses of hydrochloric acid hydrogen chloride: occurrence, preparation, purification and identification

Hydrochloric acid can be converted into chlorine by heating with :

  1. calcium oxide

  2. lead [III] oxide

  3. lead [IV] oxide

  4. lead [II] oxide
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Explanation :-

In $HCl$, the chlorine atom present with $-1$ oxidation state and $Cl _2$ has zero oxidation state. It means chlorine undergoes reduction that is only possible in the presence of a strong oxidizing agent.

$\underset{agent (Pb \ in \ +4 \ state)}{\underset{strong \ oxidizing}{PbO _2}} + 4HCl \rightarrow PbCl _2 + Cl _2 + 2H _2O$