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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 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
Name the following:
Metals which forms an amphoteric oxide.
Write equations for the reactions of calcium and potassium with water.
Which gas is produced when dilute hydrochloric acid is added to a reactive metal?
The solution of Aluminium sulphate in water is .....................
(a) Green
(b) Colourless
(c) Pink
(d) Blue
Why does aluminium not react with water under ordinary conditions?
Name two metals which cannot displace hydrogen from dilute acids.
Can we keep sodium immersed under water? Why?
Write one reaction in which aluminium oxide behaves as a basic oxide and another in which it behaves as an acidic oxide.
What special name is given to substances like aluminium oxide.
Name another metal oxide which behaves like aluminium oxide.
Write the chemical equation of the reaction which takes place when iron reacts with dilute sulphuric acid. What happens when the gas produced is ignited with a burning matchstick?
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.
Name one metal more reactive and another less reactive than hydrogen.
An acidic oxide is produced by the element:
(a) Na
(b) C
(c) Ca
(d) H
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.
An element X forms two oxides XO and XO2. The oxide XO has no action on litmus solution but oxide XO2 turns litmus solution red.
(a) What is the nature of oxide XO?
(b) What is the nature of oxide XO2?
(c) Would you call element X a metal or a non-metal? Give reason for your choice.
(d) Can you give an example of element like X?
What is the cause of chemical bonding (or chemical combination) of atoms of elements?
Write the name and formula of a molecule made up of three atoms of oxygen.
Which property of metals is used for making bells and strings of musical instruments like Sitar and Violin?
Which one among the following is an acidic oxide?
