1. Solutions
Chemistry B: Module 6

2. Solutions homogeneous mixture Parts Example:
Solute – substance that dissolves
Solvent – dissolving medium
Example:
Sugar and CO2 are solutes in water for most soft drinks
What other solutes are in your favorite soft-drink?

3. Types of Solutions Depends on the state (or phase) of the solvent~
Gas – ex. Air, Nitrogen gas is the solvent
Liquid –
most common type;
water is the most common solvent;
ex. Sugar water, water is the solvent
Solid –Nitrinol is titanium dissolved in nickel, used to make braces

4. Important Vocabulary
Soluble – substance dissolves in solvent; ex. Sugar is soluble in water
Insoluble – substance does not dissolve in solvent; ex. Sand is insoluble in water
Immiscible – 2 substances that do not mix; ex. Oil and vinegar are immiscible
Miscible – 2 liquids that are soluble in each other

5. Solvation
– process of surrounding solute particles with solvent particles to form a solution
Hydration – solvation in water
“like dissolves like” – look at bonding and polarity of particles and the intermolecular forces between particles
water molecules are dipoles; the oxygen end is a little bit negative and the hydrogen end is a little bit positive.

6. Solvation of ionic compounds
water molecules collide with crystals
the attraction between water dipoles and ions is stronger than the attraction between the ions
this “pulls” the crystal apart
Watch this animation

7. Solvation of Molecular Compounds
sucrose, C12H22O11, is polar, the O-H bonds allow for H-bonding with water; oil also has O-H bonds but is nonpolar and therefore insoluble in water
Heat of solvation – overall energy change that occurs during solution formation

8. Rate of Solvation increase collisions between solute and solvent by:
agitating mixture, which increases surface area of solute
increase temperature of solvent
Increase the surface area by crushing the solute.
HEAT IT! CRUSH IT! STIR IT!

9. Solubility
Solubility – the maximum amount of solute that will dissolve in a given amount of solvent at a given temp and pressure; expressed as grams of solute per 100 g of solvent
A solution that contains the maximum amount of dissolved solute for a given amount of solvent at a specific temp and pressure is saturated.
A solution that contains less dissolved solute for a given temp and pressure than a saturated solution is unsaturated.
A solution which contains more dissolved solute than a saturated solution at the same temp is supersaturated.

10. Solubility Diagrams Amount of water is 100g
Dissolves better in Cold water=exothermic-feel HOT
All gases are exothermic
Represents saturated solutions at the given temperature
Lines curving up are ENDOTHERMIC

11. Solubility Diagrams, cont using KNO3 as an example
Any point on the line is SATURATED
Any point below the line is UNSATURATED
Solute that is dissolved above the line is SUPERSATURATED
If you have a point above the line not dissolved that’s the excess sitting on the bottom of a saturated solution
Take the QUIZ

12. Effect of Temperature on Solubility
Solids – solubility increases as temperature increases
Gases, Acids, and Bases – solubility decreases as temperature increases

13. Effect of Pressure on Solubility
Only for gaseous solutions
Solubility increases as external pressure increases.

14. Energy Terms~must know these!
exothermic – a system that gives off energy, feels warm
(gas, acid, base) + water  solution + heat
endothermic – a system that absorbs energy, feels cool
solid + water + heat  solution

15. Math of Solutions Easy formula
Molarity-mole of solute in one liter of solution
The greater the value the greater the concentration of solute
Easy formula

16. Molality
Molality=moles of solute per kg of solvent

17. Dilution Problems
Use the following formula to determine the amount before or after adding solvent:

18. Bonus problem! Bonus Problem (+10 points)
Show all work and turn in on a separate sheet of paper!
If 10.4 grams of solute in 164 g of phenol lowers the solution’s freezing point to 36.3 °C from the solvent’s freezing point of °C, what is the molar mass of the solute.
(Kf of phenol = FP of phenol = °C)