Question

How is energy transferred when sodium chloride is dissolved in water?

Answer 1

The making of bonds releases energy. The breaking of bonds requires energy.

Explanation:

When sodium chloride dissolves in the water, the following reaction occurs:

`NaCl(s) + "excess "H_2O rarr [Na(OH_2)_6]^(+) + [Cl(OH_2)_(4-6)]^(-)`

The `[Na(OH_2)_6]^(+)` species is the so-called aquated complex, which we would normally represent as `Na^+(aq)`. Bond formation of these ion-dipole bonds almost precisely equals the energy required required to disrupt the ionic lattice. Dissolution of sodium chloride is thus slightly endothermic.