Q23 of 79 Page 3

In Frasch process of digging out sulphur from a deep underground, how has it made possible to life sulphur from the bed to surface of each? What is the basic principle on which extraction of sulphur is based? Draw a neat and labelled diagram. Besides elemental form, in what compound forms is sulphur found. Give two physical properties of sulphur.

  1. In the Frasch process in order to bring out sulphur from the underground deposits, a hole of about 30 cm diameter is bored up to the sulphur bed.
  2. It is based on the principle that sulphur has a comparatively low melting point of 1150 or 3880 due to which it can be melted by introducing super-heated water in the underground sulphur deposits.
  3. This mixture of molten sulphur and water is then brought out by the force of hot, compressed air.
  4. Three concentric pipes A, B, C of different diameters are put down in the boring.  


  5. The three pipes are arranged one inside the other as shown in the above figure. Super-heated water under pressure is forced down through the outermost pipe A. The heat given out by hot water melts the underground sulphur.
  6. A jet of hot, compressed air is then sent down through the innermost pipe C. The force of compressed air brings the mixture of molten sulphur and water through the central pipe B. The sulphur water emulsion is kept in settling tanks when sulphur gets cooled and separates from water in the form of a yellow solid. The sulphur obtained by this method is 99.5% pure.

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21 State briefly how you will extract iron from its ore. Draw a neat and labelled diagram. Write all the chemical reactions involved in it. 22 Write the chemical formula for the following.
a) Alumina b) Silica c) Rust d) Oleum e) Slag f) Sodium amalgam g) Bauxite h) Haematite. 24 The copper vessels used in homes are found to be coated with green colour. Answer the following.
a) What is the chemical composition of the green coating?
b) Why do copper vessels form such a green coating?
c) What is the name of the phenomenon, responsible for the green coating?
d) Copper vessels are best cleaned with tamarind or lemon juice, but not with soap. Why? 25 Give reasons for the following
i. Silicon counts among metalloids
ii. Carbon is not used for making aluminium from aluminium oxide.
iii. For making hydrogen by reaction with hydrochloric acid, granulated zinc is preferred to a block of zinc.