Factors Affecting Solution Formation

Types of SolutionsSolubility Curves

Unit 8 – Solutions

Chapter 15

Solution FormationFactors that affect solution formation

• Temperature– Usually an increase in temperature

means and increase in solubility (more solute dissolves)• Except for gases. The increase in

temperature means less solubility for a gas.

• *A higher temperature means the solute will dissolve faster due to more collisions between solvent and solute molecules

Increase in Surface Area• Solute that is crushed in smaller pieces will

dissolve faster than big chunks. More contact between solute and solvent.

Agitation• Mixing of solution will increase number of

collisions of solute and solvent molecules.

• In general, anything that increases contact between solute and solvent will increase solubility!

Pressure- (For Dissolved Gases Only)

• Increase in pressure will increase the solubility of a gas in a liquid

Types of Solutions• Unsaturated Solutions – Solutions that can

still dissolve more solute.

• Saturated Solutions – Solutions that have dissolved as much as they possibly can. Any more solute added would settle at the bottom and not dissolve.

• Supersaturated Solutions - Solutions that contain even more dissolved solute than saturated solutions. – Can happen when some solvent evaporates from

a saturated solution. It will form crystals when the solution is disturbed.

SOLUBILITY CURVES

• Solubility – The amount of solute required to form a saturated solution with a specific amount of solvent at a specific temperature.

• Expressed as

grams of solute/100 grams of solvent

Examples• The solubility of NaCl in water at

80oC is 40grams/100 grams of water

• How many grams of NaCl should dissolve in 250 grams of water at 80oC?

250 grams H2O 40 grams NaCl

100 grams H2O

= 100 grams NaCl will dissolve

Things to remember when reading a solubility curve graph

• The line of the curve represents a saturated solution for that temperature.

• Above this line means you have a supersaturated solution.

• Below this line means you have an unsaturated solution.

1. If you dissolve 40 grams of KCl in 100 grams of water at 80oC, what type of solution will you have?

-Unsaturated

2. If you dissolve 70grams of NH4Cl in 100 grams of water at 50oC, what type of solution will you have?

- Super saturated

3. If you dissolve 20 grams of KClO3 in 100 grams of water at 50oC, what type of solution will you have?

- Saturated (on the line)