Metals and Non- Metals / part III / reactivity Series of metals and Extraction of metals from their ores

*Reactivity Series :-  

Reactivity series of metals

The Arrangement of elements according to their reactivity is called reactivity series.

* Reaction Of Metals with water.

Metal react with water to form metal hydroxide and hydrogen gas is released

Metal +water ------->metal hydroxide +hydrogen gas

Na (s)  + cold H2O (l) ------------>NaOH (aq)+H2(g)
K (s) + cold H2O (l) ---------> KOH (aq) + H2 (g)

Note:- 

Some Metals react with cold water:
Sodium and Potassium are the metals which reacts with cold water.

*Metals reacts with hot water

Some Metals react with hot water:

Calcium and Magnesium are the metals which reacts with hot water.

Ca (s) + hot H2O (l)  --------> Ca(OH)2 (aq)
Mg(s) + hot H20 (l) ----------> Mg(OH)2 (aq)

Note:- 

Some react with steam:Metals like Iron, Zinc and Aluminium react with steam

*when iron reacts with steam :

Fe (s)+steam H2O(l)--------->Fe3O4(s) +H2 (g)

Some elements don't reacts:-
Elements below hydrogen in reactivity series like copper, mercury, silver, gold and platinum are less reactive Metals hence cannot displace Hydrogen from acids.

* Order of reactivity of Metals 
Na> Mg> Zn> Fe> Cu

*Reaction of Non-Metals with water:
Non-Metals do not react with water because they are electron acceptor and cannot donate electron to Hydrogen.

*Reaction of Metal with dilute acids:-

Metals react with acids to form  salt and hydrogen gas is released

Example:-
 H2So4(aq) + Zn(s) ---------->ZnSo4(aq) + H2 (g)

Reason:- Metals below hydrogen  in the reactivity series can’t displace hydrogen of acids because they are less reactive then hydrogen.

For displacing, they need to donate electrons to hydrogen but it is not possible because they are themselves electron acceptors.

✓Metallurgy:-

metals have good reactivity. So, they generally occur in combined state but few metals that are less reactive occur in free state like platinum ,gold etc.

*Minerals: 

Different kind of minerals

Anything that is found in earth’s crust is called mineral.

* Ores:-

Different kind of ores

             The mineral from which metal can be extracted is called ore.

Note:- All ores are minerals but all minerals are not ores.

*Different Types of Ores:

Oxide ores
Halide ores
Sulphide ores
Carbonate ores
✓Ores of Some Metals:

Aluminium: Bauxite ore, cryolite ore
Iron: Haemtite ore,  magnetite ore
Copper: Copper pyrite, copper glance
Zinc: Zinc Blende
Mercury: Cinnabar

*Metallurgy:-

          It is the process of extracting metal from its ore.
Occurrence of ore:-
Metals at the bottom e.i, lower reactive series elements are least reactive and are found in free state.
Example:- Au, Ag, PT and Cu

Copper and Silver are found in combined state as Sulphides or Oxide Ores.

Ores of medium reactive elements are found in Oxides and Sulphides forms in nature .

Metals of Top of the activity series are never found in free state.
Example:- K, Na, CA, Mg, and Al

The metals in the middle of the activity series are moderately reactive and are found in earth crust as many as Oxides, Sulphides or Carbonates.
Example:- Zn, Fe, Pb etc.

*Various steps involved in metallurgy are as follows -

1) Concentration of ore or Enrichment of Ores
2) Oxidation of ore
3)Reduction of ore
4) Refining

1) Concentration of ore or Enrichment of Ores:-
          Ores contain large amount of impurities such as soil, sand etc and are called gangue. These impurities must be removed from ore for the extraction of metal which is based on physical and chemical properties of gangue and ore.

The process of removing these impurities from ore is called Concentration of Ore or Enrichment of Ore.

*Oxidation of ore:-

It is the process of converting concentrated ore into metal oxide.

*The methods involved are calcination and roasting

a) Calcination
b) Roasting
Calcination: 

It is the process of heating ore in absence of air to convert Metal Carbonate  ore to Metal oxide.

Example : ZnCo3 (s)--------->ZnO (s)+ Co2 (g)
Reduction
ZnO (s) + C (s) --------> Zn (s) + O2 ( g)

This method is used only for carbonate ores

Roasting:- it is the process of  conversion of Metal Sulphide Ore into a metal Oxide by heating ore in presence of air

For Example: When Cinnabar( HgS) is heated in air, it's convert into mercuric oxide and further mercuric oxide then reduced to mercury on further heating.
HgS( s) + O2 (g) ------> HgO (s) + SO2 (g)
HgO (s) heated-------> Hg (s) + O2 (g)

*Displacement reaction use for extraction of metal from ore.

The higher reactive Metals such as Sodium , Calcium, Aluminium etc. are used as reducing agent because they can displace metals of lower reactivity from their compound.
Example:-
When Manganese oxide is heated with Aluminium powder.

3MnO2 (s) + 4Al (s)-------> 2Al2O3 (s) + 3Mn (l)

The displacement reaction are highly exothermic thus the amount of heat evolved is so large that the metals are in molten state.
Thermit reaction:-
The displacement reaction of iron(III) oxide [Fe2O3] with aluminium .

Fe2O3 (s) + 2Al ( s)-------> 2Fe (l) + Al2O3 (s) + Heat

Use :-
The molten metal is use in joining railway tracks or cracked machine parts.

✓Extration of metals from high reactive series

The metals of higher reactive series elements are very reactive which cannot be obtain by heating with carbon because these metals have more effinity for oxygen than carbon. These metals obbtained by electrolytic reduction .
Example:- Na, Mg are obtained by the electrolysis of their molten chloride.

✓ Electrolytic refining:-

Electrolytic refining of copper

Metals like Zn, Sn,Ni etc are refined electrolytically in which Impure metal is made anode and thin strip of pure metal is made cathode. A solution of metal salt is used as electrolyte.
*On passing current through the electrolyte pure metal from anode dissolves into the electrolyte and deposited on cathode. The soluble impurities go into the solution  where as impure impurities settle down at bottom of anode called anode mud.
✓ Corrosion

Rusting of Iron

Corrosion of copper

The process in which the metals like silver become black when exposed in air as it reacts with sulphur in air and form silver sulphide
Copper react with moist cabon dioxide in air and form copper sulphide ( green)
Iron when exposed to moist air it form brown substance called rust.

*Prevention of Corrosion

Rusting can be prevented by painting, oilinggreasing , galvanising, Chrom plating anodising and making alloys
Galvanising :- It is the method of protecting steel and iron from rusting by coating thin layer of zinc
Alloying:- This process is use to improve the  properties  of metals.It is the homogeneous mixture of two or more metals or metal and non metals.
Ores of metals:-
1) Brass alloy of Copper and zinc
2) Bronze alloy of Copper and Tin
3) Solder alloy of Lead and Tin

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