Chemistry EXTRACTION OF TIN

Please Wait... While Loading Full Video

EXTRACTION OF TIN

Extraction of Tin :

`text(Occurrence of Tin)` : Tin does not occur in nature in the native state. Its chief ore is cassiterite or tin stone (`SnO_2`).

`text(Extraction of tin from tin stone)` : The ore is crushed, washed and concentrated magnetically to remove magnetic impurities of tungstate of iron (wolframite, `FeWO_4`) and manganese. The concentrated ore is roasted to remove sulphur and arsenic as their oxides. The roasted ore is then subjected to smelting i.e. ore is mixed with anthracite (coke) in the ratio `1 :4` and little limestone (flux) and heated in a reverberatory furnace.

`SnO_2 + 2C overset(1500- 1600K)-> Sn +2CO`;

`CaCO_3 -> CaO + CO_2`

`CaO + SiO_2 -> CaSiO_3`

The molten metal is tapped out from the bottom of the furnace and cast into blocks. The tin thus obtained is called block tin and contains impurities of `Fe`, `Pb` and `Cu` etc. The crude metal is finally refined by either liquation, poling or electro-refining.

In electro-refining, impure metal is made the anode while a sheet of pure metal acts as the cathode. The electrolyte consists of stannous sulphate `SnSO_4` containing little `H_2SO_4` and hydrofluorosilicic acid (`H_2SiF_6`).

On passing current, tin dissolves from the anode and passes into the electrolyte while an equivalent amount of tin from the electrolyte gets deposited on the cathode.

`text(Occurrence of Tin)` : Tin does not occur in nature in the native state. Its chief ore is cassiterite or tin stone (`SnO_2`).

`text(Extraction of tin from tin stone)` : The ore is crushed, washed and concentrated magnetically to remove magnetic impurities of tungstate of iron (wolframite, `FeWO_4`) and manganese. The concentrated ore is roasted to remove sulphur and arsenic as their oxides. The roasted ore is then subjected to smelting i.e. ore is mixed with anthracite (coke) in the ratio `1 :4` and little limestone (flux) and heated in a reverberatory furnace.

`SnO_2 + 2C overset(1500- 1600K)-> Sn +2CO`;

`CaCO_3 -> CaO + CO_2`

`CaO + SiO_2 -> CaSiO_3`

The molten metal is tapped out from the bottom of the furnace and cast into blocks. The tin thus obtained is called block tin and contains impurities of `Fe`, `Pb` and `Cu` etc. The crude metal is finally refined by either liquation, poling or electro-refining.

In electro-refining, impure metal is made the anode while a sheet of pure metal acts as the cathode. The electrolyte consists of stannous sulphate `SnSO_4` containing little `H_2SO_4` and hydrofluorosilicic acid (`H_2SiF_6`).

On passing current, tin dissolves from the anode and passes into the electrolyte while an equivalent amount of tin from the electrolyte gets deposited on the cathode.

Properties of Tin :

It is a soft white metal, malleable and ductile and can be rolled into sheets and foils. When heated in air, it forms `SnO_2`, with `S` it forms `SnS_2` and with `Cl_2` it gives `SnCl_4`. It dissolves in hot concentrated alkalies evolving `H_2` gas

`Sn + 2NaOH + H_2O -> Na_2SnNO_3 + 2H_2`

and reacts with `HNO_3` to give metastannic acid `(H_2SnO_3)`

`Sn + 4HNO_3 -> H_2SnO_3 + 4NO_2 + H_2O`

With dil. `HCl` or `H_2SO_4` tin reacts liberating `H_2` gas

`Sn + 2HCl -> SnCl_2 + H_2O`

With hot conc. `H_2SO_4` tin reacts to give `SO_2` gas

`Sn + 2H_2SO_4 (conc.) -> SnSO_4 + SO_2 + 2H_2O`

Tin is widely used for plating iron and brass vessels to resist corrosion. Tin foils are also used for wrapping cigarettes and making food containers.

It is a soft white metal, malleable and ductile and can be rolled into sheets and foils. When heated in air, it forms `SnO_2`, with `S` it forms `SnS_2` and with `Cl_2` it gives `SnCl_4`. It dissolves in hot concentrated alkalies evolving `H_2` gas

`Sn + 2NaOH + H_2O -> Na_2SnNO_3 + 2H_2`

and reacts with `HNO_3` to give metastannic acid `(H_2SnO_3)`

`Sn + 4HNO_3 -> H_2SnO_3 + 4NO_2 + H_2O`

With dil. `HCl` or `H_2SO_4` tin reacts liberating `H_2` gas

`Sn + 2HCl -> SnCl_2 + H_2O`

With hot conc. `H_2SO_4` tin reacts to give `SO_2` gas

`Sn + 2H_2SO_4 (conc.) -> SnSO_4 + SO_2 + 2H_2O`

Tin is widely used for plating iron and brass vessels to resist corrosion. Tin foils are also used for wrapping cigarettes and making food containers.

SiteLock