by • 14/07/2011 • 9th class ChemistryComments (1)931

Q1) How is iron manufacture by blast furnace?

A)extraction of iron: iron metal is gradually extracted from its oxide ores by reducing them with carbon in the from of coal and coke.
the charge, consisting of roasted ores, coke and limestone is fed into the top of the furnace. a preheated blast of air at about 1500c is blown into the furnace under pressure near to the bottom. the blast oxidizes the coke to carbon dioxide.
the reaction is highly exothermic considerable heats librated which raises the temperature about 1900c in this region as the carbon dioxide passes upwards it react with more coke to form carbon monoxide.
the formation of carbon monoxide is an endothermic process and the temperature in this region falls to about 1100c .the carbon monoxide thus produced serves as the main reducing agent in the upper region of the furnace.

the liquid iron runs downward to the bottom of the furnace and is with drawn through a tap hole.
the lime stone which was added to the charged is known as flux. it decomposes to form CaO and carbon dioxide.CaO react with the gangue(mostly silica and some alumina)to form their respective salts. they are known as slag.
the slag floats as the molten iron and is run off which molten iron is seen into sand moulds where it cools down to solid blocks called pig iron.


Q2) what is rusting?
ans) rusting of iron:- when an iron is exposed to air and moisture its surface is gradually corroded and converted into a brown mass. this brown mass is known as rust.


Q3)how is rusting controlled by the catholic protection and electroplating?
ans)cathodic protection:-to protect theironobject from corrosion by this method the object is connected to a block of metal such as gene or aluminum which is comparatively more reaction than iron when corrosion starts an electrochemical reaction takes place and only the more reaction prevented from rusting.
electroplating:-electroplating is used to cover iron object chromium, nickel or other less easily corroded metals. this process used to prevent decorative as well as protective coatings.
alloying:-rusting is often prevented by converting the iron into an alloy such as stainless steel.
painting:- paint is generally used for coating large object such as ship, bridges and soon.
grease and oil:- grease and oil is used for coating the moving parts of machinery.




Q4) how copper is extracted?
ans)extraction of copper:- the extraction of copper from its ore involved concentration roasting,melting,reducing and electrical refining.

1) concentration:-the ore is concentrated by a process known as froth froth floation the mixture of the mineral and impurities are mixed with water and oil. pure oil or creosote oil are usually used. air is blown into the mixture and the oil forms a froth which floats to the surface. the ore particles tend to get coated with oil and are carried to the surface with it. the froth along with the mineral particles is skim men off from the top to get the concentrated.
2) roasting:- the concentrated ore is roasted in a furnace. part of the sulphur is converted to sulphur dioxide and other impurities such as arsenic which are burnt off.
3) smelting:-in the smelting process the roasted ore is mixed with sand and heated strongly until it melts. the remaining impurities react with the silica to form a slag of molten silicates. this is removed from the top of the molten mass which remain is called matte and consist of mixture of CuS2 and FeS.
4) reduction:-reduction of the matte is carried out in a converter where air is blown through. the molten material and molten material and molten copper is obtained. more sand is added as a flux to remove the iron in the form of an iron silicate slag.
5) refining:- blistered copper is refined by electrolysis. blistered copper, in the anode and a plate of pure copper is made cathode. a solution of copper sulphate act as the electrolyte. the impure copper dissolves at the anode and is deposited in the form of pure copper at the cathode.


Q5) write 3 chemical properties of copper?
ans) chemical properties:-
1) copper react with oxygen, sulphur and halogens under suitable condition to from the corresponding compound.
2) it react with acid which contain oxygen, such as dilute nitric acid and concerned sulphuric acid.
3) copper displace less reaction metal, such as silver another precious metals like give and iron.

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