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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.
‘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’.
Write the electron-dot structures for sodium, oxygen and magnesium.
Explain the following reaction with the help of a balanced chemical equation:
Magnesium reacts with hot water.
Name two metals which form amphoteric oxides.
Name the metal which has been placed just below copper in the reactivity series.
Give reason for the following:
Blue colour of copper sulphate solution is destroyed when iron filings are added to it.
What is the nature of the oxide Na2O? What happens when it is dissolved in water? Write the chemical equation of the reaction involved.
What happens when magnesium reacts with very dilute nitric acid? Write an equation for the reaction involved.
What is the action of water on magnesium ? Write equation of the chemical reaction involved.
Write the equation for the reaction of Iron with dilute hydrochloric acid.
Name the products formed. Also indicate the physical states of all the substances involved.
Name one metal which displaces copper from copper sulphate solution and one which does not.
A basic oxide will be formed by the element:
(a) K
(b) S
(c) P
(d) Kr
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?
If A, B, C, D, E, F, G, H, I, J and K represent metals in the decreasing order of their reactivity, which one of them is most likely to occur in a free state in nature?
Choose the correct alternative and rewrite the following:
Reaction of iron nails whith copper sulphate solution is an example of _____________________
Aluminium is used for making cooking utensils. Which of the following properties of aluminium are responsible for the same?
(i) Good thermal conductivity
(ii) Good electrical conductivity
(iii) Ductility
(iv) High melting point
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)?
The substance that will be flattened on beating with a hammer is ______.
