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प्रश्न
What is meant by 'rusting of iron'? With the help of labelled diagrams, describe an activity to find out the conditions under which iron rusts.
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उत्तर
Iron objects, kept in moist air for a long period of time, react with moist air to form a reddish brown crumbling substance called rust (hydrated iron (III) oxide, Fe2O3. X H2O, where X is the number of moles of water that differs). This corrosion of iron metal by reacting with moist air is called the rusting of iron.
Conditions essential for the rusting of iron:
1. Presence of air (oxygen)
2. Presence of water (moisture)
Let us do an activity to prove that moist air is necessary for the rusting of iron.
Experiment: Take three test tubes and place a dirt-free iron nail in each of these test tubes (refer to the figure below). In the first test tube, anhydrous calcium chloride is added and the test tube is closed. In the second test tube, distilled water and a layer of oil is added and the test tube is closed with a cork. In the third test tube, tap water is added. The nail is dipped into water in such a way that a part of it is exposed to the damp air present inside the test tube.
Observation:
(i) The nails in the first and the second test tube do not rust.
ii) The nail present in the third test tube rusts.
Conclusion:
Hence, we can conclude that both air and water are necessary for the rusting of iron.
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संबंधित प्रश्न
Give two examples of alloys with their chemical composition.
Which metals do not corrode easily?
Which of the following methods is suitable for preventing an iron frying pan from rusting?
Choose the correct answer from the options given below:
Heating an ore in a limited supply of air or in the absence of air at a temperature just below its melting point is known as
A. Smelting
B. Ore-dressing
C. Calcination
D. Bessemerisation
What special name is given to their corrosion of iron?
The chemical reaction involved in the corrosion of iron metal is that of:
(a) oxidation as well as displacement
(b) reduction as well as combination
(c) oxidation as well as combination
(d) reduction as well as displacement
Explain why, iron sheets are coated with zinc.
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.
Complete the process of iron rusting by filling the blanks. Suggest a way to prohibit the process.
The iron rust is formed due to........................... reaction. Different
regions on iron surface become anode and cathode.
Reaction on anode region :
`F_e(s) → Fe^(2+) (aq) +2e^-`
Reaction on anode region :
`O_2(g) + 4H^+(aq) +............................ → 2H_2 O (l) `
When Fe2+ ions migrate from anode region they react with ................... to form Fe3+ ions.
A reddish coloured hydrated oxide is formed from ............... ions. It is called rust.
`2Fe_(3+) (aq) + 4H_2O(l) → ................. + 6H_+(aq) `
A way to prevent rusting ..................................................................
What are the adverse effects of corrosion?
Write three methods of preventing rusting of iron.
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 reason for the following:
A suspension of rust is basic in nature.
Rusting of iron : Fe2O3 : : corrosion of copper : ______
Bronze : _______ : : Stainless steel : Fe + Cr + C
Find the odd one out and give its explanation.
State two conditions necessary for rusting of iron.
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?
Galvanisation is a process used to prevent the rusting of which of the following?
Explain the following:
Lime water turns milky on passing carbon dioxide gas into it.
