Tag: electroplating and its application

Questions Related to electroplating and its application

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

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

  1. outer metal surface is removed

  2. metal becomes thin

  3. outer corroded layer will be removed

  4. all of the above

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Correct Option: C
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.

If copper is kept open in air, it slowly loses its shining brown surface and gains a green coating. It is due to the formation of:

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

  1. $CuCO _3$

  2. $CuSO _4$

  3. $CuCO _3.Cu(OH) _2$

  4. $CuO$

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Correct Option: C
Explanation:

Copper reacts with $CO _2$ present in the air and forms a green coating on its surface due to the formation of basic copper carbonate.


$2Cu+O _2+CO _2+H _2O\rightarrow CuCO _3.Cu(OH) _2$

So, the correct option is $C$

According to the electrochemical concept, corrosion occurs at :

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

  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

Show answer
Correct Option: A
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.

Mark the correct statement:
a) Damp air alone supplies both things needed for corrosion.
b) Ordinary water supplies both air and water for corrosion.
c) Moist air can't provide both things.

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

  1. a, b

  2. a, c

  3. b, c

  4. All of the above

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Correct Option: A
Explanation:

Damp air supplies both the things needed for rusting of Iron. Ordinary water has some air dissolved in it. So, it can do the same.

What is corrosion?

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

  1. When metal is gradually destroyed through chemical reactions

  2. When metal is created through chemical reactions

  3. When a redox reaction takes place

  4. When a metal is destroyed after exposure to a gas

  5. When a solid is destroyed through chemical reactions

Show answer
Correct Option: B
Explanation:

Corrosion occurs when a redox reaction takes place.

Corrosion is a natural process, which converts a refined metal to a more chemically-stable form, such as its oxide, hydroxide, or sulfide. It is the gradual destruction of materials by chemical and/or electrochemical reaction with their environment.
It also gradually destroys the element through chemical reactions

Hence, the correct options are $A$ and $C$

If copper is kept open in air, it slowly loses its shining brown surface and gains a green coating. It is due to the formation of:

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

  1. $CuSO _{4}$

  2. $CuCO _{3}$

  3. $Cu(NO _{3}) _{2}$

  4. $CuO$

Show answer
Correct Option: B
Explanation:

The green coat is due to the basic copper carbonate formation and is a mixture of copper carbonate and copper hydroxide $(CuCO _3$ and $Cu(OH) _2)$.

Which of the following metals has been used for building boats because it has resistance to corrosion by sea water?

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

  1. Copper

  2. Nickel

  3. Fungsten

  4. Titanium

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Correct Option: D
Explanation:

Titanium is used for building boats.

Inert metals which do not react with gases in air seen as oxygen are found to be non-corrosive.
It is corrosion resistance because it forms stable, protective, oxide film when $Ti$ is exposed to oxide film.

In the rusting of iron, iron has been:

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

  1. oxidised

  2. reduced

  3. vaporised

  4. decomposed

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Correct Option: A
Explanation:
In corrosion, metal is oxidised by loss of electrons to oxygen to form metal oxide. In rusting of iron, at one spot of the iron object oxidation occurs and that spot behaves as an anode.
Anode:    $Fe(s)  →  Fe^{2+}(aq) + 2e^-  $
Cathode: $4e^- + 4H^+(aq) + O _2(aq)  →  2H _2O(l)$

Iron nails rust fast when used for fixing plates or strips of aluminium on a building. Similarly, a water pipe made of iron corrodes faster when connected to a pipe of copper. This happens because of the?

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

  1. Greater wetting of iron

  2. Easier flow of electrons to iron

  3. Higher rusting power of iron

  4. Chemical reduction of iron

Show answer
Correct Option: C
Explanation:

This is due to higher rusting power of iron.

When iron pipe is connected to copper corrosion is caused by self induced current created. The current is generated due to difference in electrical potential. The water act as a weak electrolyte.

The presence of $CO _2$ in the atmosphere results in:

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

  1. rusting.

  2. dusting.

  3. electroplating.

  4. freezing.

Show answer
Correct Option: A
Explanation:

The presence of $CO _2$ in the atmosphere will do iron oxide rusting. When a drop of water hits an iron object, two things begin to happen almost immediately. 

First, the water, a good electrolyte, combines with carbon dioxide in the air to form a weak carbonic acid, an even better electrolyte. As the acid is formed and the iron dissolved, some of the water will begin to break down into its component pieces - hydrogen and oxygen. 
The free oxygen and dissolved iron bond into iron oxide, in the process freeing electrons.