Explain the following
(a) The reactivity of a piece of aluminium metal decreases if it is
dipped in HNO3
(b) Carbon cannot reduce the oxides of Na or Mg
(c) NaCl does not conduct electricity in solid state whereas it
does conduct electricity in aqueous solution as well as in
molten state
(d) Necessity of galvanisation of iron articles
(e) Metals like Na, K, Ca and Mg are never found in their free
state in nature.

NCERT Class X
Science - Exemplar Problems

Chapter_SAMPLE QUESTION PAPER-I

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Answers

2015-05-31T18:56:16+05:30
A)When aluminium is dipped in nitric acid a layer of aluminium oxide is formed on the metal. This happens because nitric acid is a strong oxidizing agent. The layer of aluminium oxide prevents further reaction of aluminium. Due to this, the reactivity of aluminium decreases. B)Sodium and magnesium have higher affinity towards oxygen than towards carbon because these are highly reactive metals. Hence, carbon cannot reduce the oxides of Na or Mg. C)Ionic compounds do not conduct electricity in solid state but they conduct electricity in aqueous solution and in molten state. Hence, this property is shown by sodium chloride. D)Iron articles are galvanized to prevent rusting of iron. After galvanization, the layer of zinc works as protective layer. E)Metals; like Na, K, Ca and Mg are highly reactive metals and hence they are not found in their free state in nature. Plz mark it as best answer. Sorry yrr. It's is combined. Pls view it correctly and write
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