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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
Why do we apply paint on iron articles?
Which metals do not corrode easily?
What are alloys?
Give reasons:
Platinum, gold and silver are used to make jewellery.
Explain how painting of an iron gate prevents it from rusting.
Explain why rusting of iron objects is faster in coastal areas than in deserts.
What type of chemical reaction is involved in the corrosion of iron?
In one method of rust prevention, the iron is not coated with anything. Which is this method?
Fill in the following blank with suitable word:
The corrosion of iron is called ................
Fill in the following blanks with suitable words:
Tiffin boxes are electroplated with .............. but car bumpers are electroplated with ............... to protect them from rusting.
Fill in the following blanks with suitable words:
............ and .............. are necessary for the rusting of iron.
Name five methods of preventing rusting of iron.
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?
If copper is kept exposed to damp air for a considerable time, it gets a green coating on its surface. This is due to the formation of:
(a) hydrated copper sulphate
(b) copper oxide
(c) basic copper carbonate
(d) copper nitrate
No chemical reaction takes place when granules of a rusty-brown 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.
(a) What could the solids A and B be?
(b) What are the products C and D most likely to be?
(c) Write the chemical equation for the reaction between A and B leading to the formation of C and D. Mention the physical states of all the reactants and products in this equation and indicate the heat change which takes place.
(d) What is the special name of such a reaction? State one use of such a reaction.
(e) Name any two types of chemical reactions under which the above reaction can be classified.
Four metals P, Q, R and S are all obtained by the reduction of their oxides with carbon. Metal P is used to form a thin layer over the sheets of metal S to prevent its corrosion. Metal Q is used for electroplating tiffin boxes made of metal S whereas metal R is used in making car batteries. Metals Q and R form an alloy called solder. What are metals P, Q, R and S? How have you arrived at this conclusion?
Name the metal which is a constituent of blood pigment?
Corrosion can be an advantage in some case.Explain ?
Write scientific reasons.
Lemon or tamarind is used for cleaning copper vessels turned greenish.
Identify the process shown in the diagram and explain it in short
What are the adverse effects of corrosion?
Answer the following question.
List two properties of alloys.
Give reason.
A wooden article should be polished.
Give reason.
Copper and brass utensils should be tinned.
Give reason for the following:
A suspension of rust is basic in nature.
Which of the following method is used to prevent the accumulation of greenish layer on brass due to corrosion?
_______ forms a green colour in the water.
Find the odd one out and give its explanation.
Write scientific reason.
On exposure to air, silver articles turn blackish after some time.
Write scientific reason.
Coins are made from metals and alloys.
Explain concept with example/explain with the help of a balanced equation.
Corrosion
Draw a neat labelled diagram.
Electroplating
The process of coating the surface of the metal with a thin layer of zinc is called ______
Amalgam is an alloy of ____________.
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:
Explain the following:
Lime water turns milky on passing carbon dioxide gas into it.
Explain the chemical reactions in rusting of iron.
| 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.
