- No. v. What do you mean by a fraction of petroleum?
Answer. Fraction of petroleum means a part of petroleum that is a mixture of hydrocarbons having different number of carbon atoms in it. Each fraction has its specific name, boiling range and usage in daily life.
- No.1. What role is played by pine oil in the concentration process?
Answer. In the concentration process of copper ore, pine oil is added. Pine oil wets the ore particles and being lighter, they float over the surface in the form of a froth that can be skimmed. While, the gangue particles are moisturized by water. They settle down at the bottom. Hence the pine oil plays the role of separator of ore particles from gangue particles.
- No.2. Name the various metallurgical steps.
Answer. The important metallurgical steps are:
- concentration of the ore;
ii extraction of the metal, and
iii refining of the meta
- No.3. How roasting is carried out?
Answer. Roasting: It is a process of heating the concentrated ore to a high temperature in excess of air. For example; copper pyrite (CuFeS2) is strongly heated in excess of air to convert it into a mixture of cuprous sulphide and ferrous sulphide (Cu2S + FeS). While impurities sulphur, phosphorus arsenic etc. react with oxygen to form volatile oxides. Such as
2 CuFeS2(s) + O2(g) ———> Cu2S(s)+ 2FeS(s)+ SO2(g)
- No.4. Explain process of electro refining.
Answer. Refining the impure metal by electrolysis is the most widely used process of refining metals. The impure slab of the metal is made the anode, while a pure thin sheet of metal is made the cathode. For example, electrolytic refining of copper is carried out in an electrolytic tank having copper sulphate solution as shown in figure below:
On passing the electric current through the solution, anode (impure copper) dissolves to provide Cu2+ ions to the solution. These Cu2+ ions are discharged by gaining of electrons from the cathode.
Thereby copper atoms deposit on the cathode, making it thick block of pure copper metal as is shown in figure. The impurities like gold and silver settle down as anode mud.
- No.5. What are advantages of Solvay’s process?
(i) It is a cheap process as raw materials are available at very low prices.
(ii) Carbon dioxide and ammonia are recovered and reused.
(iii) Process is pollution free, because the only waste is calcium chloride solution.
(iv) Sodium carbonate of very high purity is obtained.
(v) Consumption of fuel is very less since no solution is to be evaporated.
- No.6. What is the principle of Solvay’s process?
Answer. Principle of Solvay’s Process lies in the low solubility of sodium bicarbonate at low temperature, i.e. at 15°C. As a result it precipitates when CO2 is passed through an ammonical solution of NaCl called ammonical brine.
Na+(aq) + HCO3–(aq) NaHCO3(s)