Chemistry · Science General

Metallurgical Processes

1,436 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 - 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

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

Which of the following statements is/are incorrect ?

  1. Rust is $Fe _{2}O _{3}$

  2. Zn - Cu cell is called Daniell cell.

  3. Saline water slows down rusting.

  4. Pure metals undergo corrosion faster than impure metals.
Reveal answer Fill a bubble to check yourself
A,C,D Correct answer
Explanation

Correct statements are given below:

a. Rust is $Fe _{2}O _{3}.xH _{2}O$.
b. Correct.
c. Saline water fastens the rusting.
d. Pure metals undergo corrosion slower than impure metals.

Hence, options A, C and D are correct options

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

The presence of electrolytes ................ the rate of corrosion. 

  1. increases

  2. decreases

  3. sharply decreases

  4. does not effect
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The presence of electrolyte increase the concentration of electron and thus increasing the mobility of electron due to which rate of corrosion increases.

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

Aluminium is more reactive than iron. But aluminium is less easily corroded than iron because:

  1. aluminium is a noble metal

  2. oxygen forms a protective oxide layer on aluminium surface

  3. iron unergoes reaction easily with water

  4. iron forms both mono and divalent ions
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Corrosion resistance of aluminium is due to formation of thin layer of aluminium oxide that forms when metal is exposed to air and prevents further oxidation. It is called as protective passivation.

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

Which of the following statement is not true?

  1. metals produce a ringing sound when struck hard

  2. copper doesn't get rusted

  3. coal and sulphur are soft and dull in appearance

  4. magnesium and phosphorous burn vigorously in air
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Copper gets oxidized to form green oxide layer in the presence of air but this is not rusting, this layer is known as patina means tarnishing of copper into bluish green layer.

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

Lead pipes are readily corroded by:

  1. water

  2. acetic acid
  3. conc. $H _2SO _4$
  4. dil. $H _2SO _4$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Corrosion of lead is strongly accelerated by traces of acetic acid. Acetic acid in the presence of oxygen rapidly attacks lead and produces very soluble lead(II) acetate which precludes the use of lead to process or store wine or fruit juice.

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

When a corroded metal object is rubbed by a sand paper then:

  1. outer metal surface is removed

  2. metal becomes thin

  3. outer corroded layer will be removed

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

The metals lose their shine and become dull when exposed to air for a long time. Due to the formation of oxides, when the surface is rubbed by a sand paper, then the outer corroded layer is removed.

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

According to the electrochemical concept, corrosion occurs at :

  1. anodic area of metal

  2. cathodic area of metal

  3. both cathodic and anodic areas of metal

  4. neither cathodic area nor anodic areas of metal
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Corrosion can be defined as the deterioration of materials by chemical processes. 

Of these, the most important by far is electrochemical corrosion of metals in which the oxidation process $M \rightarrow M^+ + e^-$ is facilitated by the presence of a suitable electron acceptor. This is possible because metals are conductive and so, the electrons can flow through the metal from the anodic to the cathodic regions. 
Metallic corrosion occurs when metal atoms are oxidized and subsequently leave the metal lattice as ions. The oxidation reaction of the metal is referred to as the anodic half-reaction. The areas on a metal surface where oxidation occurs are referred to as anodes.

Option A is correct.