SOLUBILITY

Let’s Review some Solubility vocabulary! The ability to dissolve a substance in water. solubility: solute: Solvent: solution: Water is considered the universal solvent! Why? Water is the universal solvent because it will dissolve many things in it! The substance being dissolved. The substance that the solute is being dissolved in. A mixture made of solute(s) and a solvent.

Let’s do the solubility conductivity Lab! Solutions Some solutions are good conductors of electricity. To understand conductivity of solutions we need to conduct an experiment with ionic and covalent solutions. Let’s do the solubility conductivity Lab!

Solubility If you make a solution of sugar, Kool-Aid and water. What is the solvent and solute in this solution. The sugar and Kool-Aid are the solutes and the water is the solvent in this solution. Digging further… Can you get the sugar and Kool-Aid back? If so, what would you do? Evaporate the water to leave behind the sugar and Kool-Aid Is this a physical or chemical property? Physical Property

Conductivity of Solutions Ionic bonds tend to break up in water, covalent bonds don't. This is b/c the charged ions are attracted to the opposite partial charges on the water molecules. So the ionic compound is pulled apart in the water!!! When the ionic bonds break, they leave the ions floating around in the water as charged particles. That's important…

Conductivity of Solutions It’s important b/c electricity is carried by charged particles. So, a good conductor of electricity would be a sodium ion, Na+, or a chlorine ion, Cl-. (See where this is going?) Covalent bonds do not have charged particles. So solutions that have an ionic compound as a solute will conduct electricity well! And solutions that have a covalent compound as a solute will NOT conduct electricity at all.

Solubility Curves (Graphs) Solubility varies from one substance to the next. Therefore, we have solubility curves… graphs of solutes regarding the amount that will dissolve in a certain amount of solvent.

How much KNO3 can be dissolved at 70oC in 100 ml of water? 120 g

Reading a Solubility Curve Where the solutes cross they are equally soluble at that temperature. Amount of Solute dissolved is on the Y-AXIS) (Remember: Temp. is on the X-AXIS

At what temperature are the solutes equally soluble? 28 oC (If you said 38, you were reading the wrong axis!)

How much KNO3 can be dissolved at 50oC in 100 ml of water? About 75 g (Don’t forget units!!!)

Q: At what temperature can 52 g of KCl be dissolved? 80 o C (Don’t forget units!!!)

Q: How much NaCl can be dissolved at 60oC? 39 g

Solubility Curve For Gases The solubility curve for gases are the opposite of the solubility curve for solids. The solubility of a gas decreases as the temperature increases. Solid graph Gas graph

Which substances on the graph are gases? NH3 and HCl

Q: How much NH3 can be dissolved at 65oC? 20 g

At what temperature can 60 g of HCl be dissolved? 45 oC

Saturated Solutions Saturation is when something has dissolved in a solution and no more of it will dissolve under normal circumstances. It has reached equilibrium.

Unsaturated Solutions Unsaturated is just before the equilibrium is reached, so you can keep dissolving the substance into the solution.

Supersaturated Solutions Supersaturated is when you change the conditions so that you can dissolve more of the substance into the solution than it normally would. If the solution is brought back under normal conditions, it will spit back out the substance. (Cocacola is an example of a super saturated solution of CO2, when a bottle is opened it will attempt to reach equilibrium again by bubbling and fizzing. When it does reach equilibrium it becomes flat) Another example is Rock Candy

Super saturated Saturated Unsaturated

Factors that Affect Solubility There are three main factors that will cause the rate of solubility (how fast a solute dissolves) to increase. Can you guess what they might be? Stirring Heating the solution Increasing the surface area of the solute