The lattice energy of KCl is 202 kcal / mol . When KCl is dissolved in water 2 kcal / mol is absorbed. If the hydration energies of K + and Cl − are in the ratio 2 : 3 ; then Δ H hydration of K + is

Question

The lattice energy of KCl is 202 kcal / mol . When KCl is dissolved in water 2 kcal / mol is absorbed. If the hydration energies of K + and Cl − are in the ratio 2 : 3 ; then Δ H hydration ​ of K + is

TestHub · Accepted Answer

Concepts: Lattice energy, hydration energy, enthalpy of solution.

$Δ H_{so l} = Δ H_{l a tt i ce} + Δ H_{h y d r a t i o n}$ .

$2 = 202 + Δ H_{h y d r a t i o n}$ .

$Δ H_{h y d r a t i o n} = - 200 kcal/mol$ .

Ratio $K^{+} : C l^{-} = 2 : 3$ .

$2 x + 3 x = - 200 ⟹ 5 x = - 200 ⟹ x = - 40$ .

$Δ H_{h y d r a t i o n} (K^{+}) = 2 x = - 80 kcal/mol$ .

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