question_answer

A sulphate salt of group 2 element of the Periodic Table is a white, soft substance, which can be moulded into different shapes by making its dough. When this compound is left in open for sometimes, it becomes a solid mass and cannot be used for moulding purposes. Identify the sulphate salt. Why does it show such behaviour? Give the reaction involved. Or (a) What is meant by metallurgy? (b) State two steps associated with extraction of copper from its ore. (c) How is impure copper purified by electrolytic refining? Draw a labeled diagram to illustrate it.  

Answer:

Salt is , Plaster of Paris, white soft substance.                                   (1) It can be dough, moulded into different shapes, as 2 molecules of CaS04 share 1 molecule of  molecule.                                                                                              (1)                                                      (1) When it is left in open, it becomes solid mass  (gypsum) which cannot be used for moulding purposes as it is hard solid mass.                                (2) Or (a) The collection of all the processes involved in extracting metal from its ore is called metallurgy. (b) (i) Froth-floatation process (ii) Roasting (c) Impure copper is taken as anode whereas pure copper is taken as cathode. Copper sulphate solution  is taken as electrolyte. When electric current is passed, impure copper changes to ions which gain electrons at cathode and change into pure copper. Impurities are left behind as anode mud. At anode At cathode