Tag: changes around us

Questions Related to changes around us

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

Show answer
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.