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प्रश्न
Compare roasting and calcination.
Distinguish between:
Roasting - Calcination
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उत्तर
| Roasting | Calcination | |
| 1. | This method is generally used for sulphide ores | This method is generally used for carbonate ores. |
| 2. | In this method, ores are heated in excess of air. | In this method, ores are heated in a limited supply of air. |
| 3. | In roasting, generally sulphur dioxide gas is evolved. | In calcination, generally carbon dioxide gas is evolved. |
| 4. | In this method, sulphide ores are oxidized to form metal oxides. E.g. \[\ce{2ZnS + 3O2 -> 2ZnO + 2SO2 \uparrow}\] |
In this method, carbonate ores decompose to form metal oxide. E.g. \[\ce{ZnCO3 -> ZnO + CO2 \uparrow}\] |
APPEARS IN
संबंधित प्रश्न
Tinning : Tin : : Galvanizing : _________
Explain the term “corrosion” with an example. Write a chemical equation to show the process of corrosion of iron.
Name any three objects (or structures) which are gradually damaged by the corrosion of iron and steel.
State two conditions for the rusting of iron.
In one method of rust prevention, the iron is not coated with anything. Which is this method?
The corrosion of iron is called ______.
The corrosion of copper produces a ______ coating of basic copper carbonate on its surface.
______ and ______ are necessary for the rusting of iron.
What is the corrosion of iron known as?
What are the constituents of stainless steel?
State under what conditions corrosion is faster ?
Write scientific reasons.
Lemon or tamarind is used for cleaning copper vessels turned greenish.
What is done to prevent corrosion of metals?
Choose the correct alternative and rewrite the following:
Iron is _____________________.
Give reason.
An iron article should be given a coat of paint
Give reason.
A wooden article should be polished.
Give a reason why rust turns moist red litmus blue.
Write a short note on Alloying.
Observe the following picture and answer the following questions:
- What is rust?
- Write the chemical formula of rust.
- Write the reaction of oxidation of iron at the anode.
- Write the reaction of oxidation of iron at the cathode.
- What is corrosion?
Which of the following method is used to prevent the accumulation of greenish layer on brass due to corrosion?
Stainless steel is an alloy of _______.
Match the columns.
| Group A | Group B |
| 1) Electroplating | a) Pressure cooker |
| 2) Anodising | b) Silver plated spoons |
| c) Coating of tin on copper | |
| d) Coating of Zinc on iron |
Write the name.
Method used to present corrosion of copper.
Write scientific reason.
On exposure to air, silver articles turn blackish after some time.
Draw a neat labelled diagram.
Anodizing
Observe the following diagram and give answers.
- Name this method of prevention of corrosion.
- For prevention of which metal this method is used?
- What is used as anode in this method?
Give solutions by giving examples of corrosion?
Which among the following alloys contain mercury as one of its constituents?
Marble’s popularity began in ancient Rome and Greece, where white and off-white marble were used to construct a variety of structures, from hand-held sculptures to massive pillars and buildings.
The substance not likely to contain CaCO3 is:
Alloys are homogeneous mixtures of a metal with a metal or non-metal. Which among the following alloys contain non-metal as one of its constituents?
Generally, when metals are treated with mineral acids, hydrogen gas is liberated but when metals (except Mn and Mg), treated with HNO3, hydrogen is not liberated, why?
A man painted his main gate made up of iron, to
- prevent it from rusting.
- protect it from sun.
- make it look beautiful.
- make it dust free.
Which of the above statement(s) is/are correct?
In ______ process a layer of molten tin is deposited on metals.
