Tag: changes around us

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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

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?

  1. $Ag$
  2. $Cu$
  3. $Co$
  4. $Zn$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

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

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

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?

  1. only A

  2. only B

  3. only A and B

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

Ethanoic acid (acetic acid) is completely miscible with water in all proportions because it forms hydrogen bonds with water molecules. Adding 2 ml, 4 ml, or 8 ml of water to 2 ml of ethanoic acid will result in a homogeneous clear solution in every test tube.

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

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

  1. basic copper carbonate and sulphate

  2. copper oxide

  3. copper sulphide

  4. copper nitrate
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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.