Give reasons:
(a) Metals like $Na, K, Ca$ and $Mg$ are never found in their free state in nature.
(b) Iron loses its lustre over time whereas gold does not.

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Solution

(a) These metals are highly reactive and thus readily react with air and water to form their compounds.
[1 Mark]
(b) Iron moderatley reacts with air to form its oxide. The oxide forms a layer over the iron metal. Hence it loses its lustre over time.
[0.5 Marks]
Gold being quiet unreactive metal does not react with air easily and hence retains its shine.
[0.5 Marks]

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Question 61
Explain the following:

(a) Reactivity of $Al$ decreases if it is dipped in ${HNO}_{3}$ .
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(c) $NaCl$ is not a conductor of electricity in the solid state whereas it does conducts electricity in aqueous solution as well as in molten state.
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Give reasons: (a) Metals like Na, K, Ca and Mg are never found in their free state in nature. (b) Iron loses its lustre over time whereas gold does not.

Give reasons:
(a) Metals like $Na, K, Ca$ and $Mg$ are never found in their free state in nature.
(b) Iron loses its lustre over time whereas gold does not.