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ExamsJEE AdvancedChemistry

Which one of the following statements about alkali and alkaline earth metal properties is INCORRECT?

  1. Among all alkali metal cations, Cs+ has the greatest degree of hydration in aqueous solution.
  2. Among the alkali metals Li, Na, K, and Rb, lithium has the highest melting point.
  3. Among alkali metal cations in aqueous solution, Li+ has the highest ionic mobility.
  4. The first ionisation potential of lithium is lower than that of sodium.

Correct answer: Among all alkali metal cations, Cs+ has the greatest degree of hydration in aqueous solution.

Solution

Cs+ is the largest alkali metal cation with the lowest charge-to-radius ratio, so it has the weakest ion-dipole interaction with water and is the LEAST hydrated among alkali metal ions. The claim that Cs+ is most hydrated is therefore incorrect.

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