Physical Properties, purification and Alloys of Copper for std 11 & 12

Copper Metal

COPPER
Copper is one of the metals known for a long time. Extraction of copper from its ores was known even in 5000 B.C.. It is a transition element with atomic number 29 and mass number 64. its symbol is Cu. Its electronic configuration is 

Copper electronic configuration

In our country copper ores occur in Karnataka, Garval region of Himalayas, Rajsthan, Sikkim amd also in Bihar. These oress also occur in Southern Africa, United States of America, Russia, China, Mexico ad Chilli. 

Extraction from copper pyrites : 

the finely powdered ore is mixed with pine oil and water in a large tank. The sulphide ore mixes with oil and forms a thin film. Oil does not have affinity for earthly materials. The materials other than the ore particles are wetted by water. When air is bubbled through the mixture, forth containing the particles of copper ore floats on top of water and can be skimmed off easily. This method, used to concentrate copper ore, is called frothflotation.

The ore is separated and roasted in a current of air. Copper sulphide and ferrous oxide are formed.

The product is mixed with sand and is heated in a furnace. Ferrous oxide forms ferrous silicate; this is removed as liquid slag. The remaining copper sulphide when roasted in air, forms cuprous oxide (Cu2O).

At this stage, supply of air is stopped. Cuprous oxide reacts with cuprous sulphide to form molten copper.

Copper in the liquid state is allowed to cool. As it solidities dissolved sulphur dioxide comes out and blisters are formed on the surface of copper. Hence copper so obtained is called blister copper which is impure. It is subjected to purification.

Purification of copper :
Purification of copper is done by electrolytic refining. A set of thick impure copper plates are connected together and dipped in copper sulphate solution taken in a tank. Copper sulphate is the electrolyte. A set of thin pure copper plates are connected together and dipped into the same solution such that the impure copper plates are interposed between the pure copperplates (Fig). 

Purification of Copper

The set of pure copper plates is made cathode and the set of impure copper plates is made anode. This is done by connecting the sets to appropriate terminals of a battery. On passing direct current copper at the anode dissolves and get deposited on the cathode. The mass of cathode plates increases and that of anode plates decreases. Copper so obtained is 100 % pure.

Physical properties of copper :
Copper is a rose red heavy metal. It is malleable and ductile. It is a very good conductor of electricity and heat. Thermal conductivity of copper is next only to the thermal conductivity of silver. It has high melting point and high boiling point.

Alloys : 

Alloy is a homogeneous mixture of (a) two or more metals, or (b) metals and non-metals. The properties of alloys are different from the parent elements. An alloy is called a solid solution. The homogeneous mixture is produced in molten state and then solidified. Alloys are widely useful because of their special properties.

Alloys of copper : 

Some important alloys of copper with their components and uses are listed below.

Alloys of Copper.

Reaction of metals with dilute hydrochloric sulphuric nitric acid

Dilute Acids reacts with metal

Reaction of metals with dilute hydrochloric acid : 

Metals react with dilute hydrochloric acid to produce hydrogen with the formation of their respective metallic chlorides.

Experiment 6 :
Take small pieces of magnesium, zinc, iron and copper in separate test tubes. Add 10 ml of dilute hydrochloric acid to each of them. Observe the reactions that take place. Magnesium, zinc and iron react with dilute hydrochloric acid to produce hydrogen. 

Reaction of Mg ,Zn, Fe with dilute acids

Metals usually react with hydrochloric acid. But there is difference in the reactivity. In the above reactions which appear to be similar, magnesium reacts readily compared to zinc and copper. Noble metals do not react with hydrochloric acid at all.

Reaction of Mg, Zn, Fe, Cu with dilute Hydrochloric acid

The reactivity of magnesium is higher than that of zinc. Hence it reacts with hydrochloric acid more vigorously. The reactivity of zinc is lower than that of magnesium. Hence the reaction with zinc is slower. Iron takes more time to react with dilute hydrochloric acid as it has the lowest reactivity among the three.

Reaction of metals with dilute Nitric acid :
Metals produce hydrogen with very dilute nitric acid (iron is an exception) along with metallic nitrates. 

Reaction of Zn, Mg with Dilute Nitric acid

Metals produce nitrates and nitric oxide with moderately concentrated nitric acid.

Reaction of Copper wtih Concentrated Nitric acid

Metals produce metallic nitrates and nitrogen dioxide with concentrated nitric acid. 

Reaction of Copper wtih Concentrated Nitric acid

Reaction of metals with dilute Sulphuric acid :
Just like dilute hydrochloric acid, dilute sulphuric acid also produces hydrogen with the formation of their respective metallic sulphates.

Reaction of Mg, Zn, Fe with  Dilute sulphuric acid

Reaction of metals with chlorine : 

When heated aluminium powder is sprinkled in a jar of chlorine reaction takes place to form aluminium chloride. During the reaction flashes are seen in the gas. 

Reaction for Aluminium Powder

Iron and copper react with chlorine to form their respective chlorides.

Reaction of iron and copper with Chlorine

From the above examples it can be inferred, that, metals normally react with chlorine to form their respective chlorides. But the reactivity is different.

Metals properties ores Alloys extraction of irons for std 11 & 12

Properties, ores, Alloys of Metals.

Properties of metals
Copper-ores and extraction of copper
Alloys of copper
Iron and its properties
Ores of iron and extraction of iron
Alloys. 

Review

Elements are classified into metals and non-metals.
Metals are normal temperatures exist as solids, except mercury and gallium which are liquids.

Metals are good conductors of hear and electricity.
Generally metals are malleable, ductile and hard.
Metals have a tendency to donate electrons and hence they are electro positive.
Metals displace hydrogen gas from dilute acids.

INTRODUCTION
Properties of metals are different from that of non-metals. Most of the elements are metals. The crust of the earth is the biggest source of metals. Some soluble salts of metals are found in sea water. The atoms in a metal are bound together by metallic bonds.

CHEMICAL PROPERTIES OF METALS
Let us consider the reactions of metals with oxygen of air, chlorine, water and acids.

Reaction with oxygen of air :
Metals generally react with different components of the air. Different metals react in different ways under different conditions. They react with oxygen of air to produce their respective oxides. The following experiments will help you in understanding the reactions.

Experiment 1 :
Cut a small piece of sodium and place it on a watch glass. Do not do this without the supervision of your teacher. Observe the interior of the metal which has a shining surface. After sometime it turns dull and finally becomes powder. This powder is sodium carbonate. Sodium reacts with the component of air gradually to produce sodium carbonate. Sodium does not react with kerosene; this the reason for preserving sodium in kerosene.

Reaction of Sodium with Air

When sodium burns in excess of oxygen, it produces sodium peroxide .

Reaction of Sodium with Excess of Oxygen

Ex 1 Fig: Do not do this without the supervision of your teacher.

Sodium converts in Sodium Carbonate

Experiment 2 : 

Hold a piece of magnesium ribbon with tongs. Burn it in a flame. Magnesium burns brilliantly in air forming magnesium oxide. 

Magnesium burns - Magnesium Oxide develops

Magnesium Ribbon heated

Magnesium Oxide develops on end of  Ribbon

Experiment 3 :
Take a foil of copper and heat it in a flame. Allow the foil to cool. After sometime a black layer is seen on the copper foil. The black layer so produced is an oxide of copper. 

Copper Burns -  Oxide of Copper developes

Copper foils heated

Copper foils - Oxide of Copper developes

Experiment 4 :
Take three new iron nails. 

Beaker with Anhydrous Calcium

Place one of them in a beaker containing anhydrous calcium chloride (Fig). 

Close the first beaker containing anhydrous calcium chloride, by a watch-glass. Air in the first beaker remains dry because of the presence of anhydrous calcium chloride placed in cotton cloth. 

Beaker with Full of Water

Immerse the second nail fully in water (Fig). 

Beaker with half of water

Place the third nail half immersed in water (Fig).



Observe the nails after a few days. 

A brown layer is seen on the part of the nail which is exposed to air in the third beaker. The other two nails do not get brown coating.

Remember:

Iron is protected from rusting by coating it with zinc or by painting it . Iron pipes are protected by heating and then dipping them in molten coals tar.

Why does the nail in the last beaker turn brown ?
This shows that air and water are required for iron to rust. The rust is hydrated oxide of iron. The chemical formula of rust is 

Hydrated Oxide reaction Formula

By the above experiments it is evident that different metals react with the component of air in different manner and at different rates and different conditions. There are some metals which do not reat with the components of air at all. They are gold and platinum.

Reaction of metals with water :
When metals react with water, hydrogen is liberated.

Experiment 5 :
Take a trough containing water. Gently drop a small piece of sodium on the surface of water with the help of a tong. It floats on water with a hissing sound. Bubbles of hydrogen are liberated. Sometimes hydrogen may catch fire and burn.

Sodium reacts with water  - Hydrogen Bubbles liberated

Sodium reacts with water  - Hydrogen Bubbles liberated

This experiment shows that sodium reacts with water vigorously to displace hydrogen. Similarly potassium and calcium displace hydrogen from water.

When steam is passed over hot iron, zinc or magnesium, hydrogen is liberated along with the formation of their respective oxides. 

Zinc Oxide

Magnesium Oxide

Iron Oxide

Students need

More details:

(1) Reaction of metals with dilute hydrochloric sulphuric nitric acid 

(2) Physical Properties, purification and Alloys of Copper for std 11 & 12
(3) Extraction of Iron metals, for std 11 & 12 GSEB