The correct order of hydration enthalpies is (A) $\mathrm{K}^{+}$ (B) $\mathrm{Rb}^{+}$ (C) $\mathrm{Mg}^{2+}$ (D) $\mathrm{Cs}^{+}$ (E) $\mathrm{Ca}^{2+}$ Choose the correct answer from the options given below:

JEE Main · 2023 · 29 Jan 2023 · Shift 1 · Classification of Elements and Periodicity

The correct order of hydration enthalpies is
(A)

K^{+}

(B)

Rb^{+}

(C)

Mg^{2 +}

(D)

Cs^{+}

(E)

Ca^{2 +}

Choose the correct answer from the options given below:

(A)C > A > E > B > D
(B)E > C > A > B > D
(C)C > E > A > D > B
(D)C > E > A > B > D✓ Correct

Answer: (D)

Solution

Hydration enthalpy grows in magnitude as the ionic charge rises and as the ionic size falls, since both crowd more charge onto the ion's surface and bind the water dipoles more tightly. The two alkaline-earth ions, each doubly charged, therefore outrank the singly charged alkali ions, and within that pair the smaller magnesium exceeds calcium. Among the alkali ions the hydration enthalpy falls as the ion swells down the group,

K^{+} > R b^{+} > C s^{+}

. Collecting these, the order of hydration enthalpy is

M g^{2 +} > C a^{2 +} > K^{+} > R b^{+} > C s^{+}

JEE Main · 2023 · 29 Jan 2023 · Shift 1 · Single correct option

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JEE Main · 2023 · 29 Jan 2023 · Shift 1 · Classification of Elements and Periodicity

Solution

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