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प्रश्न
Explain why, the surface of some metals acquires a dull appearance when exposed to air for a long time.
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उत्तर
Most of the metals are reactive towards air. They react with oxygen present in the air to form metal oxides. The metal oxide formation appears on the surface of the metals as a thin layer. This thin layer formation of metal oxide on the metallic surface causes the dull appearance of the metals. Thus, the surface of some metals acquires a dull appearance when exposed to air for a long time.
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संबंधित प्रश्न
‘E’ is an element which reacts with oxygen to form an oxide E2O. An aqueous solution of E2O turns red litmus blue, so:
i. What is the nature of oxide E2O ?
ii. Write the name of element ‘E’.
Samples of four metals A, B, C and D were taken and added to the following solution one by one. The results obtained have been tabulated as follows.
| Metal | Iron (II) sulphate | Cooper (II) sulphate | Zinc sulphate | Silver nitrate |
| A | No reaction | Displacement | ||
| B | Displacement | No reaction | ||
| C | No reaction | No reaction | No reaction | Displacement |
| D | No reaction | No reaction | No reaction | No reaction |
Use the Table above to answer the following questions about metals A, B, C and D.
- Which is the most reactive metal?
- What would you observe if B is added to a solution of copper (II) sulphate?
- Arrange the metals A, B, C and D in the order of decreasing reactivity.
From amongst the metals sodium, calcium, aluminium, copper and magnesium, name the metal:
- which reacts with water only on boiling, and
- another which does not react even with steam.
What name is given to those metal oxides which show basic as well as acidic behaviour?
Complete and balance the following equation:
\[\ce{Na + O2 ->}\]
Why does aluminium not react with water under ordinary conditions?
Name two metals (other than zinc and iron) which can displace hydrogen from dilute hydrochloric acid?
Hydrogen is not a metal but still it has been assigned a place in the reactivity series of metals. Why?
Name one metal which displaces silver from silver nitrate solution and one which does not.
A basic oxide will be formed by the element:
(a) K
(b) S
(c) P
(d) Kr
Out of the following oxides, the amphoteric oxide is:
(a) Fe2O3
(b) Al2O3
(c) P2O5
(d) N2O
Which one of the following four metals would be displaced from the solution of its salt by the other three metals?
(a) Zn
(b) Ag
(c) Cu
(d) Mg
An element E forms an oxide E2O. An aqueous solution of E2O turns red litmus paper blue.
(a) What is the nature of the oxide E2O?
(b) State whether element E is a metal or a non-metal.
(c) Give one example of an element like E.
Name a metal which It does not react with any physical state of water?
A zinc plate was kept in a glass container having CuSO4 solution. On examining it was found that the blue colour of the solution is getting lighter and lighter. After a few days, when the zinc plate was taken out of the solution, a number of small holes were noticed in it. State the reason and give chemical equation of the reaction involved.
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Choose the correct alternative and rewrite the following:
Which of the following is lue in colour?
An alkali metal A gives a compound B (molecular mass = 40) on reacting with water. The compound B gives a soluble compound C on treatment with aluminium oxide. Identify A, B and C and give the reaction involved.
Which of the following property is not responsible for copper to be used as electrical conduction wires?
