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 chemistry p- block elements-i study of aluminium chloride study of aluminium structure of some compounds

Which reaction cannot give anhydrous $AlCl _3$ ?

  1. Heating of $AlCl _3.\, 6H _2O$

  2. Passing dry HCl over heated aluminium powder
  3. Passing dry $Cl _2$ over heated aluminium powder
  4. Heating a mixture of alumina and coke in a current of dry $Cl _2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Aluminium chloride reacts with water to form  hexahydrate. The anhydrous phase cannot be regained on heating as HCl is lost leaving aluminium hydroxide or alumina.
$Al\left( { H } _{ 2 }O \right) _{ 6 }{ Cl } _{ 3 }\rightarrow { Al\left( OH \right)  } _{ 3 }+3HCl+{ 3H } _{ 2 }O$

Multiple choice chemistry p- block elements-i study of aluminium chloride study of aluminium structure of some compounds

Anhydrous $AlCl _3$ is prepared by :

  1. reaction of HCl and Al metal

  2. reaction of dry HCl and heated Al metal
  3. passing $Cl _2$ gas over heated Al metal
  4. reaction of $Al _2O _3$ with dil HCl.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Answer:- (B) reaction of dry $HCl$ and heated $Al$ metal.
Aluminium chloride is manufactured on a large scale by the exothermic reaction of heated aluminium metal with dry hydrogen chloride at temperatures between $650$ to $750 ^0C$
$2Al + 6HCl \; \longrightarrow \; 2Al{Cl} _3 + 3{H} _2$
Multiple choice chemistry p- block elements-i study of aluminium chloride study of aluminium structure of some compounds

Anhydrous $AlCl _3$ fumes in air. What is the reason for it?

  1. It is hygroscopic in nature

  2. It gives out chlorine when exposed to air.
  3. It is hydrolysed in moist air giving out fumes of $HCl$.

  4. It loses water when exposed to moist air.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
White fumes are due to the presence of $HCl$ gas.

Anhydrous aluminium chloride is hydrolysed partially with the moisture in the atmosphere to give $HCl$ gas. 

This HCl combines with the moisture in the air and appears white in colour.

$Al{Cl} _3 + 3H _2O \; \longrightarrow \; Al{(OH)} _3 + 3HCl \text{(white fumes)}$

Hence, the correct answer is option $\text{C}$.
Multiple choice chemistry p- block elements-i study of aluminium chloride study of aluminium structure of some compounds

Which reaction cannot give anhydrous $AlCl _{3}$

  1. Heating of $AlCl _{3}.6H _{2}O$
  2. Passing dry $HCl$ over heated aluminium powder
  3. Passing dry $Cl _{2}$ over heated aluminium powder
  4. Heating a mixture of alumina and coke in a current of dry $Cl _{2}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Option A is correct because heating of $AlCl _{3}.6H _{2}O$ do not produce anhydrous $AlCl _{3}$ on heating

$AlCl _{3}.6H _{2}O\rightarrow Al _{2}O _{3}+HCl+H _{2}O$
Multiple choice chemistry p- block elements-i study of aluminium chloride study of aluminium structure of some compounds

Which of the following statement about anhydrous aluminium chloride is correct?

  1. Its anhydrous form is deliquescent and fumes in air.

  2. It is not easily hydrolyzed.
  3. It sublimes at $20^0C$ under vaccum.

  4. It is a strong Lewis base.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Aluminium chloride is hygroscopic, having a very pronounced affinity for water. It fumes in moist air and hisses when mixed with liquid water as the Cl ions are displaced with $H _2O$ molecules in the lattice to form the hexahydrate $AlCl _36H _2O$ (also white to yellowish in color).

It is  easily hydrolyzed.

It do not sublimes at $20^0C$ under vacuum.

It is a strong Lewis acid.(it accepts electrons)

So option A only is correct

Hence option A is correct statement.

Multiple choice chemistry p- block elements-i study of aluminium chloride study of aluminium structure of some compounds

Which one of the following processes does not yield anhydrous $ AlCl _3 $?

  1. Heating of $ AlCl _3 . 6H _2O $.

  2. Passing dry HCl over heated aluminium powder.
  3. Passing dry $ Cl _2 $ over heated aluminium powder.
  4. Heating a mixture of alumina and coke in a current of dry $ Cl _2 $.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$ 2AlCl _3 . 6H _2O \xrightarrow {\Delta} Al _2O _3 + 6HCl + 9H _2O $ .

Multiple choice chemistry introduction to acid and base neutralisations in everyday life acids and bases in daily life neutralisation reaction

Aluminum hydroxide is used for :

  1. fire extinguishers

  2. antacid

  3. water purification

  4. all of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Aluminum hydroxide is an interesting base, because it has a wide number of applications, including its use in antacids. As such, it reacts with and neutralizes stomach acid, and for that reason is found in commercial antacids. It is useful in fire extinguishers as a foaming agent. Aluminum hydroxide is also used in water purification, in dyeing garments, and in the production of certain kinds of glass.

Multiple choice chemistry introduction to acid and base neutralisations in everyday life acids and bases in daily life neutralisation reaction

In which of the following, neutralisation reaction takes place?

  1. Treatment of acid or basic salt

  2. Treatment of acidic effluents

  3. Treatments of gastic patients

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

Treatment of gastric patients, treatment of acidic effluents from factory wastes and treatment of acid/base salts, are examples of neutralization in everyday life. Hence, D

Multiple choice chemistry air and water pollution control smoke, dust and other air pollutants, acid rain air pollutants and its effects air and air pollution

Which of the following is a characteristic of hydrogen sulphide?

  1. Poisonous

  2. Flammable

  3. Explosive

  4. Pleasant smell
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
Explanation

Hydrogen sulfide is the chemical compound with the formula $H _2S$. It is a colorless gas with the characteristic foul odor of rotten eggs; it is heavier than air, very poisonous, corrosive, flammable, and explosive.

Multiple choice chemistry air and water pollution control smoke, dust and other air pollutants, acid rain air pollutants and its effects air and air pollution

What is released when hydrogen sulphide burns in oxygen?

  1. Hydrogen gas

  2. Water

  3. Sulphur trioxide

  4. Sulphur dioxide
Reveal answer Fill a bubble to check yourself
B,D Correct answer
Explanation

$2H _2S+3O _2\longrightarrow \underbrace {2SO _2} _{sulphur\quad dioxide}+\underbrace {2H _2O} _{water}$

When hydrogen sulphide burns in oxygen, formation of sulphur dioxide and water takes place.

Multiple choice chemistry study of the first element - hydrogen position of hydrogen in the periodic table hydrogen in periodic table trends in groups and periods

Hydrogen does not combine with ______.

  1. Sb

  2. Na

  3. He

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

Since Helium (He) is a noble gas and does not combines with hydrogen. Because bond formation is only favored when the final state of the two elements is more stable than their initial state. If a hydrogen atom bonded with a helium atom, neither of their 1s and 2s atomic orbital will be half/fully filled, which causes both atoms to be energetically unstable. Such compound will most likely break down immediately back to their respective atomic state.

Multiple choice chemistry study of the first element - hydrogen position of hydrogen in the periodic table hydrogen in periodic table trends in groups and periods

Hydrogen loses its electron to form $H^+$. In this respect, it resembles:

  1. halogens

  2. alkali metals

  3. transition element

  4. alkaline earth metals
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Alkali metals have one electron present in their outer shell in group I so after losing one electron they become stable ions similarly hydrogen has lone electron in its shell after losing it shares the same character as alkali metal group.