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प्रश्न
What is the difference between calcination and roasting?
Compare roasting and calcination.
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उत्तर
| Roasting | Calcination | |
| (1) | The ore is heated in the excess of air. | The ore is heated in the absence of air. |
| (2) | Volatile impurities are removed as oxides (SO2, P2O5, As2O3) and the ore becomes porous and more reactive. | Moisture and organic impurities are removed and the ore becomes porous and more reactive. |
| (3) | Sulphide ores are roasted, so SO2 is given off. \[\ce{2ZnS + 3O2 ->[800^\circ-900^\circ C]2ZnO + 2SO2}\] |
Carbonate and hydrated ores are calcined and CO2 or water vapour are given off. \[\ce{ZnCO3 -> ZnO + CO2}\] |
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संबंधित प्रश्न
M is a metal above hydrogen in the activity series and its oxide has the formula M2O. This oxide when dissolved in water forms the corresponding hydroxide which is a good conductor of electricity. In the above context, answer the following:
1) What kind of combination exists between M and O?
2)How many electrons are there in the outermost shell of M?
3) Name the group to which M belongs.
4) State the reaction taking place at the cathode.
5) Name the product at the anode.
Name one metal which is extracted by:
Reduction with carbon.
How is manganese extracted from manganese dioxide, MnO2? Explain with the help of an equation.
Define the term ore.
Name the gas produced when calamine ore is calcined.
Name two ores of zinc. Write the names of the chemical compounds present in them and give their chemical formulae.
Give reasons, why aluminum is used in:
painting electric and telegraphic poles
Give reasons, why aluminum is used in:
In aluminiothermy
Distinguish between ‘roasting’ and ‘calcination’. Which of these two is used for sulphide ores and why?
Identify the process given in following passage and draw neat labelled diagram showing the process.
Electrolysis of molten mixture of alumina (melting point > 20000C) is done in a steel tank. The tank has a graphite lining on the inner side. This lining does the work of a cathode. A set of graphite rods dipped in the molten electrolyte works as anode. Cryolite (Na3AlF6) and fluorspar (CaF2) are added in the mixture to lower its melting point upto 10000C.
Name the following:
Name two metals always find in combined state.
Write equations for each of the above metal which reacts with water.
Complete the incomplete statement with missing word:
Non-metals form acidic oxides while metals form ______.
Which one of the following is not true of metal :
Metals are good conductors of electricity.
Which one of the following is not true of metal :
Metals are malleable and ductile
State three objectives achieved during the roasting of ores.
Iron is _______.
Which of the following metals exist in their native state in nature?
(i) Cu
(ii) Au
(iii) Zn
(iv) Ag
An alloy is
