Chemistry · Science General

Metallurgical Processes

1,403 Questions

This section explores key metallurgical processes including ore concentration, pyrometallurgy, and metal refining. It also covers corrosion and the properties of refractory materials. These chemistry questions are relevant for engineering and science entrance tests.

Pyrometallurgy furnacesMetal refining techniquesCorrosion protection methodsOre concentrationAuto reduction process

Metallurgical Processes Questions

Multiple choice chemistry changes around us effects of oxidation reactions in daily life corrosion of metals electroplating and its application

Which of the following methods is suitable for preventing an iron frying pan from rusting?

  1. Applying grease

  2. Applying paint

  3. Applying a coating of zinc

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

We can prevent iron getting rusted by applying a coat of zinc or a thin coat of plastic helps to prevent rust. The process for coating metal like iron or steel with a thin zinc layer is known as galvanization.

Multiple choice chemistry changes around us effects of oxidation reactions in daily life corrosion of metals electroplating and its application
The surface of some metals, such as iron, is corroded when they are exposed to moist air for a long period of time. This phenomenon is known as __________ .

  1. Erosion

  2. Corrosion

  3. Rusting

  4. Both A and B
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The process where metals are degraded by reaction with moisture and air is called corrosion. When specifically referring to iron, it is called rusting.

Multiple choice chemistry changes around us effects of oxidation reactions in daily life corrosion of metals electroplating and its application

According to electrochemical theory of corrosion involves:

  1. cathodic dissolution of metal

  2. cathodic deposition of metal

  3. anodic dissolution of metal

  4. anodic deposition of metal
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In corrosion $Fe^{2+}$ get oxidised to $Fe^{3+}$ which takes place on anode surface.

Anode: $Fe(s)\rightarrow { Fe }^{ 2+ }+2{ e }^{ - }$
Cathod:${ O } _{ 2 }+4{ H }^{ + }+4{ e }^{ - }\rightarrow { 2H } _{ 2 }O$
Overall:$2Fe(s)+{ O } _{ 2 }+4{ H }^{ + }\rightarrow 2{ Fe }^{ 2+ }+{ H } _{ 2 }O$
             ${ 4Fe }^{ 2+ }+{ O } _{ 2 }+(2+4x){ H } _{ 2 }O\rightarrow { 2Fe } _{ 2 }{ O } _{ 3 }.x{ H } _{ 2 }O+4{ H }^{ + }$
So,$Fe^{3+}$ get deposited on metal surface.

Multiple choice chemistry changes around us effects of oxidation reactions in daily life corrosion of metals electroplating and its application

Which metal is usefull for protection of iron by corrosion?

  1. Aluminium

  2. Sodium

  3. Zinc

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

A thin layer of zinc coats other metals such as iron. It protects the iron from corrosion. Also since zinc is a more reactive metal it acts as a sacrificial metal. The oxygen in the air reacts with zinc to form zinc oxide, thus protecting the iron.

Multiple choice chemistry changes around us effects of oxidation reactions in daily life corrosion of metals electroplating and its application

Which of the following will be most easily corroded in moist air?

  1. $Zn$
  2. $Fe$
  3. $Ni$
  4. $Sn$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
When iron ( $Fe$ ) is exposed to moist air, it reacts with oxygen to form rust.

The formation of a rust is a very complex process, which is thought to begin with the oxidation of iron to ferrous ( iron"+2") ions.

Iron metal reacts in moist air by oxidation to give a hydrated iron oxide. This does not protect the iron surface to further reaction since it flakes off, exposing more iron metal to oxidation. This process is called rusting.
Multiple choice chemistry changes around us effects of oxidation reactions in daily life corrosion of metals electroplating and its application

State True or False.
Corrosion of motor cars is the major problem in the winter, when salt is spread on road to melt ice and snow.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

If two metals are made to touch under the surface of an electrolyte they constitute a short circuited cell. Corrosion is a greater problem in winter when the salts are laided as chromium and iron are the two metals and NaCl act as an electrolyte.

Multiple choice chemistry changes around us effects of oxidation reactions in daily life corrosion of metals electroplating and its application

State True or False.

Corrosion of iron is a redox process.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Rusting of iron is corrosion of iron. Rusting of iron takes place when iron corrodes in the presence of water and oxygen. It is a redox reaction whereby oxygen acts as an oxidising agent while iron acts as a reducing agent. When iron is contact with water, a simple chemical cell is formed.

Multiple choice chemistry changes - physical and chemical effects of oxidation reactions in daily life corrosion of metals electroplating and its application

Iron is not protected from rusting by:

  1. galvanization
  2. electroplating with $Ni$ or $Cr$

  3. heating the iron to redness in steam
  4. treating it with $H _{3}PO _{4}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Phosphoric acid will not form a protective coating of iron oxide on the surface of iron. A strong oxidizing agent such as nitric acid is required for this process.

Multiple choice chemistry changes around us effects of oxidation reactions in daily life corrosion of metals electroplating and its application

Iron articles rust readily whereas steel which is also mainly made of iron will not undergo corrosion.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  • One of the properties of iron is that it reacts with oxygen in the presence of moisture and gets corroded by forming rust.
  • Air contains oxygen and moisture. Hence, iron readily rust when exposed to air.
  • Steel (stainless steel, not mild steel) is an alloy of iron having the property to resist corrosion including rusting. Hence, stainless steel, though it contains iron, does not undergo corrosion. 
Multiple choice chemistry changes - physical and chemical effects of oxidation reactions in daily life corrosion of metals electroplating and its application

The technique of protecting a metal from corrosion by connecting it to a second metal (that is more easily oxidized) is called:

  1. galvanization

  2. anodic protection

  3. cathodic protection

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

In cathodic protection, the more easily oxidized metal is attached to the metal which is to be protected. This results in corrosion of more easily oxidized metal. The other metal is thus protected from corrosion.

Multiple choice chemistry changes around us effects of oxidation reactions in daily life corrosion of metals electroplating and its application

No rusting takes place in absence of moisture. 

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Rust is an iron oxide, usually red oxide formed by the redox reaction of iron and oxygen in the presence of water or air moisture. Given sufficient time, oxygen and water, any iron mass will eventually convert entirely to rust and disintegrate. No rusting takes place in absence of moisture. 

Multiple choice chemistry changes - physical and chemical effects of oxidation reactions in daily life corrosion of metals electroplating and its application

Iron can be prevented from rusting by:

  1. connecting iron to more electropositive metal a case of cathodic protection.

  2. connecting iron to more electropositive metal a case of anodic protection.

  3. connecting iron to less electropositive metal a case of anodic protection.

  4. connecting iron to less electropositive metal a case of cathodic protection.
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Explanation

Cathodic protection: A technique to control corrosion of a metal surface by making it work as a cathode of an electrochemical cell by placing in contact with the metal to be protected another more easily corroded metal to act as the anode of the electrochemical cell. Most commonly used to protect steel, water pipelines, and storage tanks.

Anodic protection: A technique to control corrosion of a metal by making it work as anode developing a passive film on the metal. It used in extremely corrosive conditions and most extensively used to store and handle sulphuric acid container.

Hence, option A and C are correct