The standard hydration enthalpies of four alkaline earth metal ions, namely Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , and Ba ²⁺ , are given in a random order as -1305 kJ mol ⁻¹ , -1921 kJ mol ⁻¹ , -1577 kJ mol ⁻¹ , and -1443 kJ mol ⁻¹ . The hydration enthalp

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The standard hydration enthalpies of four alkaline earth metal ions, namely Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , and Ba ²⁺ , are given in a random order as -1305 kJ mol ⁻¹ , -1921 kJ mol ⁻¹ , -1577 kJ mol ⁻¹ , and -1443 kJ mol ⁻¹ . The hydration enthalpy of the Mg ²⁺ ion is:

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Correct answer: B. -1921 kJ mol ⁻¹

The magnitude of hydration enthalpy depends on the size of the ion. Smaller ions have a higher charge density and thus undergo more extensive hydration, releasing more energy (more negative hydration enthalpy). The order of ionic radii for the given alkaline earth metals is Mg ²⁺ Therefore, the magnitude of hydration enthalpy follows the reverse order: Mg ²⁺ > Ca ²⁺ > Sr ²⁺ > Ba ²⁺ . Since Mg ²⁺ is the smallest ion among the four, it will have the most negative hydration enthalpy. Matching the given values, the hyd

The standard hydration enthalpies of four alkaline earth metal ions, namely Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , and Ba ²⁺ , are given in a random order as -1305 kJ mol ⁻¹ , -1921 kJ mol ⁻¹ , -1577 kJ mol ⁻¹ , and -1443 kJ mol ⁻¹ . The hydration enthalpy of the Mg ²⁺ ion is:

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