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प्रश्न
Explain why, the surface of some metals acquires a dull appearance when exposed to air for a long time.
उत्तर १
Some metals, when exposed to air for a long time, react with oxygen in the atmosphere to form a dull layer of metal oxide on their surfaces. This makes the metals look dull.
उत्तर २
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.
संबंधित प्रश्न
What changes in the colour of iron nails and copper sulphate solution do you observe after keeping the iron nails dipped in copper sulphate solution for about 30 minutes?
Write equation for the reaction of magnesium with oxygen.
How would you show that silver is chemically less reactive than copper?
Give reason for the following:
Blue colour of copper sulphate solution is destroyed when iron filings are added to it.
Write the equation for the reaction of Zinc with dilute hydrochloric acid.
Name the products formed. Also indicate the physical states of all the substances involved.
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.
Metal A burns in air, on heating, to form an oxide A2O3 whereas another metal B burns in air only on strong heating to form an oxide BO. The two oxides A2O3 and BO can react with hydrochloric acid as well as sodium hydroxide solution to form the corresponding salts and water.
(a) What is the nature of oxide A2O3?
(b) What is the nature of oxide BO?
(c) Name one metal like A.
(b) Name one metal like B.
CuSO4(aq) + Fe(s) → FeSO4(aq) + Cu(s)
FeSO4(aq) + Zn(s) → ZnSO4(aq) + Fe(s)
On the basis of the above reactions, indicate which is most reactive and which is least reactive metal out of zinc, copper and iron.
Which of the following reactions will not occur? Why not?
(a) MgSO4 (aq) + Cu (s) → CuSO4 (aq) + Mg (s)
(b) CuSO4 (aq) + Fe (s) → FeSO4 (aq) + Cu (s)
(c) MgSO4 (aq) + Fe (s) → FeSO4 (aq) + Mg (s)
Generally metals react with acids to give salt and hydrogen gas. Which of the following acids does not give hydrogen gas on reacting with metals (except Mn and Mg)?
