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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. \[\ce{ZnCO3 -> ZnO + CO2 \uparrow}\] |
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संबंधित प्रश्न
Tinning : Tin : : Galvanizing : _________
Explain why Iron sheets are coated with zinc during galvanization.
Explain the term “corrosion” with an example. Write a chemical equation to show the process of corrosion of iron.
The chemical reaction involved in the corrosion of iron metal is that of ______.
Tiffin boxes are electroplated with ______ but car bumpers are electroplated with ______ to protect them from rusting.
Why is an iron grill painted frequently?
Explain why, though aluminium is more reactive than iron, yet there is less corrosion of aluminium when both are exposed to air.
Explain why, when a copper object remains in damp air for a considerable time, a green coating is formed on its surface. What is this process known as?
Explain why, the galvanised iron article is protected against rusting even if the zinc layer is broken.
Name a common metal which is highly resistant to corrosion.
In stainless steel alloy, iron metal is mixed with ______.
Brass is an alloy of ______.
Bronze is an alloy of ______.
No chemical reaction takes place when granules of a solid, A, are mixed with the powder of another solid, B. However when the mixture is heated, a reaction takes place between its components. One of the products, C, is a metal and settles down in the molten state while the other product, D, floats over it. It was observed that the reaction is highly exothermic.
(i) Based on the given information make an assumption about A and B and write a chemical equation for the chemical reaction indicating the conditions of reaction, physical state of reactants and products and thermal status of reaction.
(ii) Mention any two types of reactions under which above chemical reaction can be classified.
Observe the following picture a write down the chemical reaction with the explanation.
What is ‘rusting’?
_______ is an alloy made from iron, carbon and chromium.
Which of the following method is used to prevent the accumulation of greenish layer on brass due to corrosion?
Corrosion of silver causes a black layer of _______.
To prevent corrosion of iron and steel _______ method is used.
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
Write a molecular formula for rust.
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?
Observe the following figure and write the answer of the question.
- Which process is shown in the figure?
- Explain the chemical reaction shown in the figure.
- Write the reactions on anode and cathode.
Galvanisation is a method of protecting iron from rusting by coating it with a thin layer of ____________.
The diagram shows the reaction between metal and dil. acid.
What is the reason for different behaviour of Mg in test tube B?
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?
Gold plated ornaments is the example of ______.
Give scientific reasons.
Silver amalgam is used for filling dental cavities.
| A process of forming a thick oxide of aluminium when aluminium is exposed to air. This coat makes it resistant to corrosion. Resistance can be improved by making a layer of oxide thinker. In this technique, the aluminium article is the anode, and the electrolyte is sulphuric acid. The anode reaction results in the formation of a black-coloured film of aluminium oxide on the anode. By putting appropriate dyes in the electrolytic solution, both coloured surface with the decorative finish is achieved. Kitchen articles like anodised such as pressure cookers, pans and frames of sliding windows are applications of this technique. |
- Name the anode and electrolyte used in this technique.
- How can we make aluminium articles made resistant to corrosion?
- Name the technique used to coat the aluminium articles.
Describe two changes that are harmful. Explain why you consider them harmful. How can you prevent them?
