Chemistry

Chemical Reactions and Processes

626 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 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.

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

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

$HCl$ gas cannot be dried by passing through:

  1. $H _{2}SO _{4}$
  2. $CaO$
  3. $P _{2}O _{5}$
  4. $CO$
Reveal answer Fill a bubble to check yourself
B,C Correct answer
Explanation

$CaO$ and $P _2O _5$ are basic in nature so when $HCl$ is based over them, they will react with $HCl$ and form Salt and water, whereas $H _2SO _4$ and $CO$ are an acidic and hence greater affinity for water. So they can be used to dry $HCl$.

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

$HCl$ is prepared by heating $NaCl$ with $conc.{ H } _{ 2 }S{ O } _{ 4 }$. But $HI$ cannot be prepared by treating $NaI$ with $conc.{ H } _{ 2 }S{ O } _{ 4 }$. Identify the reason.

  1. ${ H } _{ 2 }S{ O } _{ 4 }$ is oxidised by $HI$ and not oxidised by $HCl$
  2. $HI$ is oxidised by ${ H } _{ 2 }S{ O } _{ 4 }$ and $HCl$ is not oxidised by $HI$
  3. $HI$ dissociates on treatment with ${ H } _{ 2 }S{ O } _{ 4 }$ and $HCl$ does not dissociate
  4. Reaction of ${ H } _{ 2 }S{ O } _{ 4 }$ with $HI$ is reversible whereas with $HCl$ is irreversible
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$HCl$ is prepared by heating $NaCl$ with $conc.{ H } _{ 2 }S{ O } _{ 4 }$. But $HI$ cannot be prepared by treating $NaI$ with $conc.{ H } _{ 2 }S{ O } _{ 4 }$. Because  $HI$ is oxidised by ${ H } _{ 2 }S{ O } _{ 4 }$ and $HCl$ is not oxidised by $HI$.

Hence, option $B$ is correct.

Multiple choice chemistry phenomena around us comparison between physical and chemical changes introduction to physical and chemical changes change around us

Identify the physical change:

  1. Photosynthesis

  2. Respiration

  3. Digestion of food

  4. Melting of Wax
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Melting of wax is a physical change. In a burning candle there are both physical and chemical changes. The burning of the solid wax to form liquid wax and the evaporation of liquid wax to form wax vapour are physical changes. The burning of wax vapour is a physical change.

Multiple choice chemistry combustion and flame structure of flame flame combustion

The zone of no combustion is _______.

  1. The middle zone

  2. Outermost zone

  3. The base of the flame

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

Innermost zone is the zone of no combustion. It is also called as dark zone which is formed around the wick of the candle flame.

Multiple choice aluminium patterns and properties of metals chemistry

Which of the following statement is incorrect?

  1. $Al$ reacts with excess $NaOH$ to give $Al{(OH)} _{3}$
  2. $NaH{CO} _{3}$ on heating gives ${Na} _{2}{CO} _{3}$

  3. Pure sodium metal dissolves in liquid ammonia to give blue solution
  4. $NaOH$ reacts with glass to give sodium silicate
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Sodium aluminate is also formed by the action of sodium hydroxide on elemental aluminium which is an amphoteric metal. The reaction is highly exothermic once established and is accompanied by the rapid evolution of hydrogen gas. The reaction is written as:
$2Al+2NaOH+{ 2H } _{ 2 }O\longrightarrow 2NaAlO _{ 2 }+3{ H }$

$2NaHCO _{ 3 (S) }\longrightarrow N{ a } _{ 2 }CO _{ 3 (S) }+CO _{ 2 (g) }+{ H } _{ 2 }O _{  (l) }$  This statment is correct.

By the reaction of sodium with liquid ammonia sodium ammide can be prepared.Sodium (alkali metal)dissolves in liquid ammoia solution to form a blue solution characteristic of a solvated electron in liquid ammonia, which is conducting in nature, due to ammoniated electrons (solvated electron).
This statment is correct.

Sodium silicate liquid can also be prepared directly by dissolving silica sand under pressure in a heated aqueous solution of caustic soda (sodium hydroxide, NaOH):
$2NaOH+{ SiO } _{ 2 }\longrightarrow Na _{ 2 }O.{ SiO } _{ 2 }+{ H } _{ 2 }O$
This statment is correct.

Multiple choice aluminium patterns and properties of metals chemistry

Which of the statement about aluminium is not correct?

  1. It liberates hydrogen from acid as well as alkalies

  2. It liberates hydrogen from acid but not from alkalies

  3. It liberates hydrogen from hot alkali solution

  4. It liberates hydrogen from boiling water
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Solution:- (B) It liberates hydrogen from acid but not from alkalies

Aluminium is an amphoteric metal and hence it reacts with both acids as well as bases.
Reaction of $Al$ with acid-
$2 Al + HCl \longrightarrow 2 Al{Cl} _{3} + 3 {H} _{2}$
Reaction of $Al$ with base-
$2 Al + 2 NaOH + 2 {H} _{2}O \longrightarrow 2 NaAl{O} _{2} + 3 {H} _{2}$

Multiple choice aluminium patterns and properties of metals chemistry

Hydrogen gas will not be produced by :

  1. heated cupric oxide

  2. heated Ferric oxide

  3. heated stannic oxide

  4. heated aluminium oxide
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

When alluminium oxide is heted it liberates oxygen gas
$2Al _2O _3\rightarrow 4Al+3O _2$
So alluminium oxide on heating do not produce hydrogen gas
Hence option D is correct.

Multiple choice aluminium patterns and properties of metals chemistry

A metal X reacts with aqueous NaOH solution to form Y and a highly inflammable gas. Solution Y is heated and $CO _2$ IS poured through it. Z precipitates out and $Na _2CO _3$ is formed. Z on heating gives $Al _2O _3$. Identify X, Y and Z.

  1. $Al-X$, $NaAlO _2 -Y$, $Al(OH) _3-Z$
  2. $Al _2O _3-X$, $NaAlO _2-Y$, $Al _2CO _3-Z$
  3. $Al _2O _3-X$, $[Na _2AlO _2]^+Oh^--Y$, $Al(OH) _3-Z$
  4. Al-X, $Al(OH) _3-Y$, $Al _2O _3-Z$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Solution:-

$X + NaOH(aq) \; \longrightarrow \; Y + \text{highly inflammable gas}$
$Y + CO _2 + H _2O \; \longrightarrow \; Z + {Na} _2CO _3$
$Z \; \xrightarrow [On \; heating] \; {Al} _2O _3$
${Al} _2O _3$ is formed when $Al{(OH)} _3$ is heated. 
$2Al{(OH)} _3 \; \xrightarrow [On \; heating] \; {Al} _2O _3 + 3H _2O$
Thus Z is $Al{(OH)} _3.$
When $NaAlO _2$ is heated and $ CO _2$ is poured through it, $Al{(OH)} _3$ precipitates out and $Na _2CO _3$ is formed.
$2NaAlO _2 + CO _2 + 3H _2O \; \longrightarrow \; 2Al{(OH)} _3 + {Na} _2CO _3$
Thus Y is $NaAlO _2$
When $Al$ reacts with aqueous $NaOH$ solution, it forms $NaAlO _2 \; and \; H _2 \; \text{(Highly inflammable gas)}$
$Al + NaOH(aq) \; \longrightarrow \; NaAlO _2 + H _2 \; \text{(highly inflammable gas)}$
Thus X is $Al$.
Hence, (A) is correct answer.