22.2 enthalpy changes in solution

standard enthalpy change of solution

the enthalpy change that takes place when one mole of a solute dissolves in a solvent.

can be either exothermic or endothermic

how do ionic compounds dissolve

• in the aqueous ions, the partially positive and partially negative charges in the water are attracted towards the positive and negative ions

• the partially negative oxygen atom is attracted to the positive sodium ion

• the partially positive hydrogen atom is attracted to the negative chloride ion

2 processes that take place when a solid ionic compound dissolves in water

• the ionic lattice breaks up

• water molecules are attracted to, and surround, the ions

enthalpy change of hydration

the enthalpy change that accompanies the dissolving of gaseous ions in water to form one mole of gaseous ions