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प्रश्न
Alkali metals react with water vigorously to form hydroxides and dihydrogen. Which of the following alkali metals reacts with water least vigorously?
पर्याय
Li
Na
K
Cs
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उत्तर
Li
Explanation:
Both melting point and heat of reaction of alkali metals with water decrease down the group from Li to Cs. Although the heat of reaction of Li is the highest, but due to its high melting point, even this heat is not sufficient to melt the metal, which exposes greater surface to water for reaction. As a result, Li has the least reactivity but the reactivity increases as the melting point of alkali metals decreases down the group from Li to Cs.
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| (Metal) | (Emitted light wavelength (nm)) |
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| (c) Rb | (III) 670.8 |
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