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प्रश्न
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?
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उत्तर
- Rust is a reddish-brown coloured hydrated ferric oxide layer deposited on the surface of iron objects that are exposed to moist air.
- Chemical formula of rust is Fe2O3.xH2O.
- Anode region: \[\ce{Fe_{(s)} -> Fe^{2+}_{ (aq)} + 2e^-}\]
- Cathode region: \[\ce{Fe^{2+}_{ (aq)} -> Fe^{3+}_{ (aq)} + e^-}\]
- Metals get attacked by substances around it such as moisture, acids, etc. Metal is said to ‘corrode’ due to this attack and the process is called corrosion.
APPEARS IN
संबंधित प्रश्न
Write two methods of preventing the rusting of iron.
Which of the following methods is suitable for preventing an iron frying pan from rusting?
Explain why Iron sheets are coated with zinc during galvanization.
What special name is given to the corrosion of iron?
What type of chemical reaction is involved in the corrosion of iron?
The chemical reaction involved in the corrosion of iron metal is that of ______.
In one method of rust prevention, the iron is not coated with anything. Which is this method?
The corrosion of iron is called ______.
Explain why, though aluminium is more reactive than iron, yet there is less corrosion of aluminium when both are exposed to air.
With the help of labelled diagrams, describe an activity to find out the conditions under which iron rusts.
What are the constituents of stainless steel?
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?
In stainless steel alloy, iron metal is mixed with ______.
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.
- What could the solids A and B be?
- What are the products C and D most likely to be?
- 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.
- What is the special name of such a reaction? State one use of such a reaction.
- Name any two types of chemical reactions under which the above reaction can be classified.
Mention two uses of the following metals and non-metals
Iron
What is corrosion? What are necessary conditions for corrosion?
Identify the process shown in the diagram and explain it in short
Give reason.
A wooden article should be polished.
Explain the term – rusting and give a word equation for the formation of rust. If polished iron nails are kept in three separate test tubes, state the contents in each test tube required, to prove the conditions for rusting.
Give a reason why rust turns moist red litmus blue.
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 _______.
Pressure cooker : Anodizing : : Silver plated spoons : _______
Find the correlation:
Bronze : ______ :: Tin : Cu+Zn.
Find the odd one out and give its explanation.
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 |
Draw a neat labelled diagram.
Electrolysis
Observe the following diagram and write answers.
- Name the method.
- Explain the method.
- Give two examples of this method.
Give solutions by giving examples of corrosion?
Galvanisation is a method of protecting iron from rusting by coating it with a thin layer of ____________.
Amalgam is an alloy of ____________.
Identify the correct statement from the following:
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?
State whether the following statement is true or false:
Ships suffer a lot of damage though they are painted.
Explain the following:
Bubbles are produced when acetic acid is added to a solution of sodium hydrogencarbonate.
Give an example of a chemical reaction for the following situation:
Sound is produced
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.
