Tag: changes around us

Questions Related to changes around us

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

  1. Erosion

  2. Corrosion

  3. Rusting

  4. Both A and B

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Correct Option: B

Given,
$E _{Ag^{+}/Ag}^{\circ}  = +0.80V, E _{Co^{2+}/Co}^{\circ} = -0.28 V, E _{Cu^{2+}/Cu}^{\circ} = +0.34 V, E _{Zn^{2+}/Zn}^{\circ} = -0.76V$, 
Which metal will corrode to greater extent?

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

  1. $Ag$

  2. $Cu$

  3. $Co$

  4. $Zn$

Show answer
Correct Option: D
Explanation:

Metal having much more positive potential will Oxidise less easily and coorrode slowly and vice-versa. So, Zinc will corrode fastly.

According to electrochemical theory of corrosion involves:

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

  1. cathodic dissolution of metal

  2. cathodic deposition of metal

  3. anodic dissolution of metal

  4. anodic deposition of metal

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Correct Option: A
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.

Which metal is usefull for protection of iron by corrosion?

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

  1. Aluminium

  2. Sodium

  3. Zinc

  4. Copper

Show answer
Correct Option: C
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.

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

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

  1. $Zn$

  2. $Fe$

  3. $Ni$

  4. $Sn$

Show answer
Correct Option: B
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.

2 ml ethanoic acid was taken in test tubes - A, B and C. 2 ml, 4 ml and 8 ml of water was added to the test tubes A, B and C respectively. Which test tube will show clear solution?

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

  1. only A

  2. only B

  3. only A and B

  4. all

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Correct Option: A

Iron and rust are the same things.

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

  1. True

  2. False

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Correct Option: B
Explanation:

Iron and rust are different thing.

When iron $(Fe)$ undergoes corrosion it form iron oxide $(Fe _2O _3)$ which is nothing but a rust.

In the atmosphere of industrial smog, copper corrodes to form:

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

  1. basic copper carbonate and sulphate

  2. copper oxide

  3. copper sulphide

  4. copper nitrate

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Correct Option: A
Explanation:

Architectural structures built with copper corrode to give green verdigris (copper carbonate). It can be a mixture of carbonate and sulfate compounds in various amounts, depending upon environmental conditions such as sulfur-containing acid rain.

Rusting of iron is catalysed by :

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

  1. H$^+$ ions

  2. dissolved $CO _2$ in water

  3. O$ _2$

  4. impurities present

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Correct Option: A,B,C,D
Explanation:

The hydrogen ions and the dissolved gases such as carbon dioxide and water catalyze the rusting of iron.
Certain impurities also catalyze the rusting of iron.

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.

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

  1. True

  2. False

Show answer
Correct Option: A
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.