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प्रश्न
Generally, when metals are treated with mineral acids, hydrogen gas is liberated but when metals (except Mn and Mg), treated with HNO3, hydrogen is not liberated, why?
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उत्तर
Concentrated nitric acid is a very strong oxidising agent. When metals are treated with concentrated nitric acid the hydrogen gas that is produced during the reaction is further oxidised to water and thus hydrogen gas is not liberated.
`"Zn"("s") + 4"HNO"_3("conc".) -> "Zn"("NO"_3)_2 + 2"NO"_2("g") + 2"H"_2"O"("l")`
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संबंधित प्रश्न
Write two methods of preventing the rusting of iron.
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Fill in the following blanks with suitable words:
............ and .............. are necessary for the rusting of iron.
Explain why, the galvanised iron article is protected against rusting even if the zinc layer is broken.
Name a common metal which is highly resistant to corrosion.
No chemical reaction takes place when granules of a rusty-brown solid A are mixed with the powder of another solid B. However, when the mixture is heated, a reaction takes place between its components. One of the products C is a metal and settles down in the molten state while the other product D floats over it. It was observed that the reaction is highly exothermic.
(a) What could the solids A and B be?
(b) What are the products C and D most likely to be?
(c) Write the chemical equation for the reaction between A and B leading to the formation of C and D. Mention the physical states of all the reactants and products in this equation and indicate the heat change which takes place.
(d) What is the special name of such a reaction? State one use of such a reaction.
(e) Name any two types of chemical reactions under which the above reaction can be classified.
Mention two uses of the following metals and non-metals
Iron
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(i) Based on the given information make an assumption about A and B and write a chemical equation for the chemical reaction indicating the conditions of reaction, physical state of reactants and products and thermal status of reaction.
(ii) Mention any two types of reactions under which above chemical reaction can be classified.
Identify the process shown in the diagram and explain it in short
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State whether the statement given below is true or false. If false write the correct statement.
Either oxygen or moisture is essential for rusting.
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Observe the following diagram and write answers.
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Describe two changes that are harmful. Explain why you consider them harmful. How can you prevent them?
