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Explain why the surfaces of some metals ...

Explain why the surfaces of some metals become dull when exposed to air for sometime.

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The surface of some metals acquires a dull appearance when exposed to air for a long time due to the formation of a thin layer of oxide, carbonate or sulphide on their surface by the slow action of the various gases present in air.
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VK GLOBAL PUBLICATION-METALS AND NON-METALS-SHORT ANSWER QUESTION-I
  1. Explain why the surfaces of some metals become dull when exposed to ai...

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  2. Give two examples each of the metals that are good conductors and comp...

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  3. Name one metal and one non-met-al that exist in liquid state at room t...

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  4. A zinc plate was kept in a glass container having copper sulphate solu...

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  5. Generally, when metals are treated with mineral acids, hydrogen gas is...

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  6. Give reasons for the following : Metals replace hydrogen from dilute...

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  7. What happens when iron nail is placed in silver nitrate solution? ...

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  8. Why do metals not evolve hydrogen gas with nitric acid?

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  9. Name a metal from each case: It does not react with cold as well as ...

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  10. Which of the following reactions will not occur? Give reasons. MgSO4...

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  11. List any two observations when a highly reactive metal is dropped in w...

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  12. State the reason for the following behaviour of zinc metal: On placi...

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  13. An ore gives carbon dioxide on treatment with a dilute acid. What step...

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  14. The following reaction takes place when aluminium powder is heated wit...

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  15. What is a thermite reaction? Explain with the help of an equation.stat...

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  16. Why should the metal sulphides and carbonates be converted to metal ox...

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  17. What is 24-carat gold? How will you convert it into 18-carat gold?

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  18. What would happen to iron railings on the road side if they are not pa...

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  19. Explain why, the galvanised iron article is protected against rusting ...

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  20. Why is aluminium oxide considered an amphoteric oxide?

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