- No. vii. Mention the chemical reaction for the formation of metallic copper in the bessemerization process.
Answer. In the bessemerization process molten matte is further heated. Molten matte is mixed with sand and heated with a hot blast of air through tuyers. Ferrous sulphide is oxidized to form ferrous oxide. Which react with sand to form slag (FeSiO3) that float on the top.
2FeS(1) + 3O2(g) 2FeO2(g) + 2SO2(g)
FeO(1) + SiO2(1) FeSiO3(slag)
On the other hand, cuprous sulphide is oxidized to form cuprous oxide, which again reacts with remaining cuprous sulphide to form metallic copper.
2Cu2S(1) + 3O2(g) 2Cu2O(1)+ 2SO2(g)
2Cu2O(1) + Cu2S(1) 6Cu(s)+ SO2(g)
- No. viii. What is blister copper?
Answer. The molten metal is shifted from the converter to sand moulds and is allowed to cool. The dissolved gases escape out forming blisters on the surface of the solid copper. Therefore, it is called blister copper. It is about 98% pure copper.
- No. ix. Why anode is eaten up in electro-refining process?
Answer. Electro-refining of copper carried out in an electrolytic tank. It consists of two electrodes; anode of impure copper and cathode of pure copper metal. In the process oxidation takes place at anode. As a result, copper atoms of the anode lose two electrons at the anode and copper ion (Cu2+) dissolves into the solution.
Cu ———> Cu2+ + 2e;
Simultaneously, Cu2+ ions from the solution reduce and deposit at the cathode. The process continues by dissolving of anode and depositing of Cu2+ ions at cathode. Meanwhile, ultimately the anode is eaten up.
- No. x. What do you mean by anode mud?
Answer. In the electro-refining, of copper, anode is made of impure copper metal. It consists of impurities like gold and silver. When oxidation takes place at anode, there metallic ions dissolve in the solution. Cu2+ ions reduce and deposit at cathode while gold and silver impurities settle down as anode mud.
- No. i. Why only NaHCO3 precipitates when CO2 is passed through the ammonical brine?
Answer. When CO2 is passed through an ammonical solution of NaCl called ammonical brine only NaHCO3 precipitate due to its lowest solubility at 15°C in the presence of excess of CO2.
Na+(aq) + HCO3–(aq) NaHCO3(s)
- No. ii. Which raw materials are required for the formation of sodium carbonate?
Answer. Raw materials required for the formation of sodium carbonate are:
- sodium chloride or brine
- lime stone
- ammonia gas,
- No. iii. How CO2 is prepared in the Solvay’s process?
Answer. CO2 is prepared by heating limestone in a lime kiln. Then it is carried to carbonating tower.
CaCO3 ———> CaO + CO2