كيمياء لغات – Iron للصف الثالث الثانوى 2016

(Iron ( ₂₆Fe 

:Natural occurrence

.Iron is not found freely except meteorites -

.Iron is found as ores (iron oxide) mixed with impurities like; Silica (SiO₂), Al₂O₃ , CaO , and MgO -

Iron is the 4^th element in the earth’s crust after oxygen, silicon, and aluminum, (5% by mass). This mass increases towards the center of earth

:NB: The suitability of the ore in the extraction iron economically depends on three factors which are

.Iron percent in the ore -

.The composition of impurities in the ore -

.The type of harmful elements mixed with the ore as; sulfur, phosphorus, and Arsenic -

:Question

.Mention three factors effect on the suitability of the ore in the extraction of iron

:First session 1999: Compare between

  .Haematite and Limonite.                         – Haematite and Magnatite -

:Remark

.Magnetite is a compound behaves as a mixture of two oxides

 (so, the oxidation number of Fe in Fe₃O₄ is (+2, +3 ∴

.G.R: magnetic iron oxide is a mixed oxide

.Because when it reacts with conc. acids, two types of salts are produced

Extraction of iron from its ores

Extraction of iron or its metallurgy is the process of obtaining this metal in a form  where it can be put to practical use

.The process of extraction consists of three stages

:The ore Dressing

:The aim of ore dressing is

.Increasing the concentration of iron in the ore by removing the unwanted impurities

.Improving the properties of the ore which helps in the successive stages of extraction

.Improving chemical properties of the ore by roasting process

:Crushing process

.The aim of this process to obtain iron ore in small size that can be reduced easily

:Sintering process

.The aim of this process to convert the fine particles into bigger and homogeneous

.particles suitable for the reduction process

:Concentration and purification and of the ore

The aim of this process is to remove most of the unwanted impurities from the ore and increase the percentage of iron in it. It takes place by physical or mechanical methods

:Roasting

:It means heating the substance strongly in the air to

.a-     Dry the ore

.b-    Expel humidity

.c-     Convert the iron ore into iron oxide

.d-    Increase the ratio of iron in the ore

:Questions

.a-     Roasting of iron is a very important in the ore dressing process. But this process pollutes the environment

.Explain these pollutants in chemical equations *

.Explain how can you convert these pollutants to useful compounds *

b-    Ore dressing is important for iron ores before their reduction to remove most of impurities and improve the physical properties for the ore

Reduction of the Iron’s Ores

:Reduction process depends on the nature of reducing agent which may be

.a-     CO gas resulting from coke as Blast furnace

.b-    Mixture of (CO + H₂) resulting from natural gas as in Midrex furnace

“The Blast Furnace “High furnace

:Description of the furnace

a-       It is a structure, made of steel lined from inside by fire bricks

b-      Height: 25-35m

c-       Diameter: 1-18 m, in the widest part

d-      Iron produced: pig iron

:Scientific base

.Reduction of iron (III) oxide is by CO resulting from coke

:Operation

.(The furnace is fed with the charge (Hematite +Coke + Lime stone *

.A current of hot air, is forced and the following reactions take place *

:Role of coke

.Coke reacts with hot air and heat is produced which raise the temperature of the furnace

:Pig iron

The iron produced by the blast furnace is called pig iron that contains 95% iron, 4% carbon with small amounts of Mn, Si, P, S

:Questions

What is meant by pig iron

What is the role of coke in the blast furnace

What are the scientific bases of extraction of iron in the blast furnace

Midrex furnace to obtain Spongy iron

In this process, iron III oxide is reduced by a mixture of (CO + H₂) As in Alexandria iron and steel company in El-Dekhela.

The reducing agents (CO and H₂), are produced from natural gas by passing the natural gas (93% methane) with CO₂ and steam in special converters containing a catalyst.

Charge: Hematite _ Fe₂O₃

:Operation

The iron ore (Fe₂O₃) is introduced from the top of the furnace and the reducing gases (CO and H₂). i.e. The cycle of the reducing agent is closed

After the reduction process, the resulting gases (CO₂ and H₂O) are cooled and purified, then mixed with natural gas to be converted into reducing gases (CO and H₂). i.e. the cycle of the reducing agent is closed.  [Give Reason

Iron obtained is porous and is mixed with impurities. On hammering, impurities are separated and spongy iron is left.     [Give Reason

.Second session 98: Write short notes on spongy iron

It is iron mixed with impurities where it is produced from midrex furnace and it has holes similar to that in sponge

:Second session 99

Show by symbolic equation only, how can you extract sponge iron from iron ore

?First session 2004: What is the role of natural gas (93% methane) in Midrex furnace

To react with CO₂ and H₂O producing the reducing gases (CO and H₂) which reduce Fe₂O₃ into spongy iron

.G.R: Reducing gases in Midrex furnace has a closed cycle

:NB: The scientific bases of iron extraction from its ores in the Midrex furnace

.a-     Reduction of Hematite ore (Fe₂O₃) by the reducing mixture (CO and H₂) into iron called spongy iron

.b-    Removal of impurities by hammering the resulting iron where the impurities leave the spongy iron

:Question: Compare between reduction furnaces

Alloys

It is a substance has physical properties of metals, it is formed of two metals or more with a certain ratio as iron alloys (ferromanganese, ferrochromium) and it may consists of metal and nonmetal with a certain ratio as iron and carbon

:G.R

.Transition elements are characterized by the formation of several alloys-

    .Because the atomic radii of transition elements are relatively constant -

.Metals are used industrially in alloys not as pure metals -

    :Because alloys have new properties which differ from these of the pure metals such as

a-     Alloys resist corrosion

b-    Alloys have the ability to increase the magnetic and electric properties

c-     Alloys can be shaped easily

d-    Alloys are characterized by hardness

:Preparation of Alloys

:Melting Method

By melting the metals together by required ratio, then the molten is left to cool

:Electrodeposition method

By electrodepostion of two metals or more at the same time such as the brass alloy (Cu + Zn) that is used in plating iron handless which are placed in a solution of copper, and zinc ions

:Types of Alloys

:Interstitial Alloy: e.g.: Fe-C Alloy

a-      Pure iron as other metals is formed of crystalline lattice of metal atom in a closed packed structure

b-      On hammering the metal, a layer of atoms can slip over the other layers

c-       In the state of introducing small atom to form Alloy, when the introducing atoms are smaller than the small spaces between the metal atoms, they will fit these spaces and will lead also to change of physical properties of the metal

:Properties of Interstitial Alloy

Change malleability and ductility

Affect the melting point

Affect electric conductivity and magnetic properties

Affect the strength of pure metal

:Substitutional Alloy

.It is formed when some atoms of the crystalline lattice of the pure metal are replaced by atoms of the metal added

e.g.: (Fe, Cr) Alloy, (Gold and copper) Alloy, and (Fe, Ni) Alloy

:Conditions of Substitutional Alloy

.They have the same diameter, crystalline structure, and chemical properties

G.R: Copper Gold can form Substitutional Alloy

:(Intermetallic Alloy (Compound Alloy

It is formed when the elements forming the Alloy combine with each other chemically forming chemical compounds which are characterized by the following

a-  They are solid

b-  Chemical formula of these compounds disobeys the laws of valency such as Fe₃C which is called “iron carbide” or Cementite

c-   This Alloy can’t be formed by metals of the same group

Comparison between the three types of alloys

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