Ch. 13/14: Solutions Dissolution Factors

Dissolution process of dissolving a solute into a solvent can speed up the process

Surface Area Surface area- how much of the solute is exposed to the solvent dissolution occurs at the surface of the solute the more finely divided the solute is, the greater the surface area and the more quickly it dissolves

Agitation stirring or shaking a solution increases the rate of dissolution because the solute particles are more evenly dispersed in the solution brings fresh solute in contact with the solvent molecules

Heating As the temperature increases, the rate of dissolution increases Why? solvent molecules move faster because they have higher KE This helps to separate solute molecules from each other and evenly disperse them

Heating

Solubility For every combination of solute and solvent at a certain temperature, there is a certain amount of solute that can dissolve depends on the characteristics of solute, solvent and temperature

Solubility As solute particles dissolve, some will hit the surface of solute crystal and reattach Eventually, the rate of dissolution and recrystallation will be equal What does this create? Solution Equilibrium state in which opposing processes of dissolution and recrystallation occur at equal rates

Solution Equilbrium

Saturated Solutions Saturated Solution Unsaturated solution solution that contains the maximum amount of dissolved solute if more solute is added, it will fall to the bottom and not dissolve Unsaturated solution solution that contains less than the maximum amount of solute

Supersaturated Solutions solution that contains more than the maximum amount of solute can be created by heating up a solution and dissolving as much solute as possible must allow it to cool undisturbed will recrystallize quickly if seed crystal is added

Supersaturated Solution

Use of Recrystallization Only pure substances can crystallize Can be used as a separation technique. Crystals of KNO3 separated from an aqueous solution of KNO3 and CuSO4 (an impurity). The pale blue color of the solution is produced by Cu2+ ions, which remains in solution

Solubility Values amount of substance required to make a saturated solution usually given in grams per 100. mL of water Substance 0°C 20°C AgNO3 122 216 Ba(OH)2 1.67 3.89 Ce2(SO4)3 20.8 10.1 KCl 28.0 34.2 Li2CO3 1.54 1.33 CO2(g) 0.335 0.169