Q.3. Name the process of purification highlighted below: 1. The ore and gangue, particles have different densities. 2. Different wetting properties of ore and gangue. 3. Method employed for the purification of copper. 4. Method in which aluminium is used as a reducing agent. 5. Purification of impure alumina to pure alumina.
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Copper is purified by electrolysis . Electricity is passed through solutions containing copper compounds, such as copper(II) sulfate. The anode (positive electrode ) is made from impure copper and the cathode (negative electrode) is made from pure copper.
Answer:
1. Hydraulic washing is the process based on the difference in densities of ore and gangue particles. ... On passing air in this mixture, sulphide ore particles form light oily froth and reach the surface whereas gangue particles settle down at the bottom.
2. Froth floatation method is used for ores with different wetting properties of ore and gangue particles. On adding sulphide ore in a mixture of oil and water, the sulphide particles are wetted by oil and gangue particles are wetted by water.
3. The method used for refining of copper metal is electrolytic refining. During electrolytic refining of copper, the anode is the positive electrode and is made from impure copper blocks.
4.D. Sodium. Hint: We know that the thermite process is a process in which metallic oxides are reduced by using aluminum powder. If the mixture of aluminum and the oxide is heated, aluminum gets oxidized while the metal oxide gets reduced.
5. Reaction: NaAlO2 + 3H2O => Al(OH)3 +NaOH
Then, precipitates of aluminium hydroxide Al(OH)3 is repeatedly washed with water and heated. After this process, pure alumina or aluminium hydroxide is obtained. Later, the pure alumina is extracted through electrolysis process called the Hall–Héroult electrolysis process.