In which of the following exothermic reaction | vedclass

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Question

(D) The reaction of alkaline earth metal oxides with water is exothermic. The enthalpy of hydration (or heat of reaction) depends on the lattice energ

Vedclass · Accepted Answer

$MgO + H_2O 	o Mg(OH)_2$

Vedclass · Answer

(D) The reaction of alkaline earth metal oxides with water is exothermic. The enthalpy of hydration (or heat of reaction) depends on the lattice energy of the oxide and the hydration energy of the resulting hydroxide. As we move down the group from $Mg$ to $Ba$,the lattice energy of the oxides decreases significantly due to the increase in the size of the metal cation. Since the hydration energy of the metal ions also decreases down the group but at a slower rate than the lattice energy,the net enthalpy change (heat liberated) is highest for the oxide with the highest lattice energy. $MgO$ has the smallest cation size among the given options,resulting in the highest lattice energy. Therefore,the reaction $MgO + H_2O 	o Mg(OH)_2$ releases the most heat per mole.

In which of the following exothermic reactions,the heat liberated per mole is the highest?

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