Question

Among molten alkali metals the examples of immiscible pair is

Answer 1

The Li+ is much smaller than the other ions. For this reason, Li only mixes with Na and above 380 Celsius, and it is immiscible with the metals K, Rb and Cs, even when molten; nor will Li form sunstitutional alloys with them. In contrast the other metals Na, K, Rb, Cs are miscible with each other in all proportions.

Answer 2

Among molten alkali metals, the examples of immiscible pairs are $\[Li - K\]$, $\[Li - Rb\]$ and $\[Li - Cs\]$.

Explanation:

• The miscibility of molten metals with each depends upon their size.
• A metal smaller in size will be miscible with smaller sized metal while it will be immiscible with metals with more size.
• The size of lithium is much smaller than the size of other alkali metals.
• Due to its smaller size, it can be miscible with only Sodium ($Na$).

• It is immiscible with $\[K,\,Rb\,\]$ and $Cs$ even in the molten stage in all proportions.
• On the other hand, the alkali metals $\[Na,K,\,Rb\,\]$ and $Cs$ are found to be miscible with each other in all proportions.
• Thus, the immiscible pairs of molten alkali metals are $\[Li - K\]$, $\[Li - Rb\]$ and $\[Li - Cs\]$.

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