JEE MainChemistrys Block Elements
Match List I with List II. List I (Ion) List II (Hydration enthalpy in kJ mol ⁻¹ ) (A) Na ^+ (I) -1921 (B) Rb ^+ (II) -1305 (C) Mg ²⁺ (III) -406 (D) Ba ²⁺ (IV) -293 Choose the correct answer from the options given below:
Options
- A(A)-(IV), (B)-(III), (C)-(II), (D)-(I)
- B(A)-(III), (B)-(IV), (C)-(I), (D)-(II)
- C(A)-(I), (B)-(II), (C)-(III), (D)-(IV)
- D(A)-(IV), (B)-(III), (C)-(I), (D)-(II)
Correct answer
B. (A)-(III), (B)-(IV), (C)-(I), (D)-(II)
Step-by-step solution
The magnitude of hydration enthalpy depends on the charge density of the ion. Alkaline earth metal ions (Group 2) have a higher charge and smaller size compared to alkali metal ions (Group 1) of the same period, leading to much more negative hydration enthalpies. Thus, Mg ²⁺ and Ba ²⁺ will have the more negative values ( -1921 and -1305 kJ mol ⁻¹ ). Within a group, as the ionic size increases down the group, the degree of hydration decreases, and so does the magnitude of hydration enthalpy. For Group 2: Mg ²⁺ is sm