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JEE Main 20198 AprilMorning Shift

Exam: JEE Main
Year: 2019
Date: 8 April
Shift: Morning Shift
Subject: Chemistry
Chapter: s Block Elements

JEE Main 2019 · 8 April · Morning Shift · Chemistry · s Block Elements

The correct order of hydration enthalpies of alkali metal ions is:

The correct order of hydration enthalpies of alkali metal ions is:

Options

A $N{a}^{+} > L{i}^{+} > {K}^{+} > R{b}^{+} > C{s}^{+}$
B $N{a}^{+} > L{i}^{+} > {K}^{+} > C{s}^{+} > R{b}^{+}$
C $L{i}^{+} > N{a}^{+} > {K}^{+} > R{b}^{+} > C{s}^{+}$
D $L{i}^{+} > N{a}^{+} > {K}^{+} > C{s}^{+} > R{b}^{+}$

Correct answer

C. $L{i}^{+} > N{a}^{+} > {K}^{+} > R{b}^{+} > C{s}^{+}$

Step-by-step solution

Hydration Enthalpy

∝ {\left(+ q\right) .}_{}{( - q}_{} )

∝ \dfrac{1}{{r}^{+}} + \dfrac{1}{{r}^{-}}

As radius increases enthalpy of hydration decreases so in a group on going from top to bottom hydration enthalpy decreases.

L{i}^{+} > N{a}^{+} > {K}^{+} > R{b}^{+} > C{s}^{+}

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