Tag: changes around us

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Questions Related to changes around us

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

Which metals does not corrode easily?

  1. Gold

  2. Iron

  3. Aluminium

  4. Zinc
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In the activity series, metals are on the top of the series react and corrode easily as these metals are highly reactive like iron corrodes easily in the presence of water and air forming its oxide layer while metals present at the bottom are least reactive and do not corrode easily like gold, silver and platinum are some of them.


Option $(A)$ is correct.

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

If edible oil is allowed to stand for a long time in an iron or tin container, the oil becomes rancid.

  1. True

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

If edible oil is allowed to stand for a long time in an iron or tin container the fatty acids in the oil react with rust flakes or powder to form salts. These salts contaminate the oil and hence the oil becomes rancid. Thus the above statement is true.

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

A shiny brown-coloured element 'X' on heating in air becomes black in colour. Name the element 'X'?

  1. Sodium

  2. Calcium

  3. Copper

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

'X' is copper (Cu) and the black-coloured compound formed is copper oxide(CuO). The equation of the reaction involved on heating copper is given below:

$\underset{(Shiny\,brown\,in\,colour)}{2Cu} + O _2 \overset{Heat}{\rightarrow} \underset{(Black\,in\,colour)}{2CuO}$

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

Assertion: Rusting of Fe is quicker in saline water than in ordinary water.
Reason: Presence of $Na^+$ and $Cl^-$ ions increase the conductance of the saline water.

  1. Both Assertion and Reason are true and Reason is the correct explanation of Assertion

  2. Both Assertion and Reason are true but Reason is not the correct explanation of Assertion

  3. Assertion is true but Reason is false

  4. Assertion is false but Reason is true

  5. Both Assertion and Reason are false
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The $Na^{\oplus}$ and $Cl^{\ominus}$ present in saline water increase the conductance of the solution in contact with the metal surface. This accelerates the formation of $Fe^{2+}$ ions and hence that of rust, $Fe _2O _3 \cdot xH _2O$

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 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.