Metallurgical Processes

The process of depositing a layer of any desired metal on another material by means of electricity is called electroplating.

Metallic objects are electroplated to protect the metal underneath and to make it attractive.

Chromium does not corrode and is scratch resistant. Chromium is neither cheap nor is it easily available. Electroplating of chromium is a complex and controlled process as the chromium layer tends to peel off.

Leblanc process is an industrial process for the production of soda ash (sodium carbonate, Na₂CO₃).

1. The floatation process is the concentration method of sulphide ores. Zinc ores, mainly ZnS, are concentrated by floatation method, then roasted in air to give ZnO and SO₃.
   1. Zn is used extensively for coating for the appliances made up of corrosive metals like Fe to prevent them from rusting.
   2. Cd metal absorbs neutrons very well and is used to make control rods in nuclear reactors.
   3. The largest use of mercury is in electrolytic cells for the production of sodium hydroxide and chlorine gas at commercial level. Hence, statements 2 and 3 are incorrect.

This option is correct because the mixture of iron ore, coke and limestone is called ‘charge’. Iron ore is not pure iron oxide; it also contains an assortment of rocky material. This wouldn't melt at the temperature of the furnace and would eventually clog it up. The limestone is added to convert this into slag which melts and runs to the bottom. The heat of the furnace decomposes the limestone to give calcium oxide.

Particles of matter in the solid state have strong attractive forces between them. This force, known as the force of cohesion, keeps the particles together. Particles of iron have very strong forces of attraction, and the particles are tightly bonded to each other. So, it is difficult to overcome these forces and hence, break an iron nail. 

Since the metals like iron, copper, aluminium are hard and cannot be pressed easily, they are long lasting. Hence, these metals are used to make utensils.

In electrochemical corrosion, corrosion depends on the size of the anodic part of the metal. Smaller area of anode as compared to cathode will lead to faster corrosion.

In galvanic series, oxidation potential of metals is arranged in decreasing order of activity of a series of metals. Metals, which come first in galvanic series corrode easily. Hence, Zn will corrode at the fastest rate.

Anodizing is an electrolytic passivation process, used to increase the thickness of the natural oxide layer on the surface of metal parts. While electroplating, galvanizing and metal spraying are methods of metallic coating for protection against corrosion.

Crevice corrosion occurs due to concentration difference between two regions of the same metal component. Corrosion takes place at the part of lower concentration.

Anodic coating is done by a metal, which is situated prior to the base metal in the electrochemical series.

Desiccant method is a temporary measure of corrosion protection. Desiccant bags are intended to protect the package contents from humidity during transport and storage in order to prevent corrosion, mould growth, etc. Galvanization, tin plating and copper plating are permanent corrosion protection methods.

Magnesium is one of the most common sacrificial anodic metals. Magnesium is more positive than iron, and hence in electrochemical cell it acts as anode and iron acts as cathode.