1. Mr. Kinton Honors Chemistry
Solutions
Mr. Kinton
Honors Chemistry

3. Mixtures Combination of 2 or more substances
Does not follow the law of definite proportions
Mixtures are either homogeneous or heterogeneous
Separated by physical means
Each of the substances in a mixture are called components

4. Heterogeneous Mixtures
Do not have the same composition
Do not have do not have the same properties
Do not have a uniform appearance
Colloids and suspensions are specific types

5. Suspensions Heterogeneous mixture in which some particles settle
Able to settle due to their size and gravity acting on them
Typically will occur in a liquid medium

6. Colloids
Type of mixture where the particles dissolved are larger than normal but remain small enough to be suspended
Can occur as solids, liquids and gases
Tyndall Effect- the scattering of light by colloidal particles

7. Homogeneous Mixtures Mixture that is uniform throughout
Can be in the solid, liquid or gaseous state
Also referred to as solutions
Forms when one substance disperses uniformly throughout another
With the exception of gaseous solutions, they all contain the condensed phase

8. 7 Types of Solutions

9. Terminology for Solutions
Solvent- the component of a mixture that is present in the greatest amount.
This component does the “dissolving”
Solute- the component of a mixture that is present in a smaller amount.
This component is being “dissolved”
Solubility- The amount of solute needed to form a saturated solution in a specific quantity of solvent
Solvation- occurs when the solvent completely surrounds the solute and breaks the intermolecular forces holding the solute together
Hydration- the process of solvation when water is the solvent

10. The Solution Process

11. The Solution Process
The solute and solvent must have similar attractive forces in order for a solution to form
When a solution is formed this is simply a physical change
When a solution energy is either absorbed or it is released
Endothermic- energy is absorbed, typically non-spontaneous (positive value)
Exothermic- energy is released, typically spontaneous (negative value)
∆Hsoln = ∆H1 + ∆H2 + ∆H3
∆H1 = Separation of solute molecules
∆H2 = Separation of solvent molecules
∆H3 = Formation of solute-solvent interactions
∆Hsoln = Enthalpy change of the solution or Heat of the solution

12. Enthalpy of Solution Formation

13. Entropy The amount of disorder present in a system
Processes that increase entropy tend to occur spontaneously
Solution formation is favored when entropy increases

14. Solutions and solubility
Saturated solution- solution that is in equilibrium with the undissolved solute
Solute + Solvent Solution
Unsaturated solution- less solute is dissolved than possible for a given solvent
Supersaturated solution – solution that has been heated, additional solute has been added, and then the solution is cooled.
These solutions are extremely unstable

15. Solubility Curves X-axis gives the temperature
Y-axis tells the amount of solvent being used
Allows us to know the saturation point of specific compounds
Be sure to look at the axes in order to properly answer questions!

16. Solute-Solvent Interactions
Increase when there are stronger attractions between solute and solvent
Hence “like dissolves like”
Miscible: liquids that mix in all proportions
Immiscible: liquids that do not dissolve each other

17. Pressure The amount of force applied on a given area of an object
Only impacts gases in solution
Increasing pressure causes an increase in gas concentration

18. Temperature
Increase in temperature causes an increase in solid solubility
Increase in temperature causes a decrease in gas solubility

19. Types of Solutes Nonelectrolyte Strong Electrolyte Weak Electrolyte
A Substance that does not form ions in solution
Examples:
Hydrocarbons
Alcohols
Other Molecules
Exist mostly as molecules with a small fraction of ions also
Examples:
Weak Acids
Weak Bases
Solutes that completely or nearly exist as ions
Examples:
Strong Acids
Strong Bases
Salts- ionic compound formed by replacing the H+ of an acid

21. Concentration
The amount of solute dissolved in a given quantity of solvent or solution
The more solute that is dissolved the more concentrated the solution will be
Concentration is not the same thing as the strength of the solution
What is the difference between concentration and strength?
We will often express concentration quantitatively rather than qualitatively

22. Concentration Molarity Molality M
Molarity equals moles of solute divided by volume of solution
Units are given as mol/L
Electrolyte concentration can be expressed by the compound or the components m
Molality equals moles of solute divided by kilograms of solvent
Units are given as mol/kg
Electrolyte concentration can be expressed by the compound or the components

23. Example 1
Calculate the molarity of a solution made by dissolving 23.4 grams of sodium sulfate in enough water to make 125 mL of solution.

24. Example 2
What are the molar concentrations of each of the ions present in a .025 M aqueous solution of calcium nitrate?

25. Example 3
A solution is made by dissolving 4.35 grams of glucose in 25.0 mL of water. Calculate the molality of glucose in the solution.

26. Dilution
Process in which a stock solution is made less concentrated by adding water
Moles solute before dilution = Moles of solute after dilution
M1V1=M2V2
For diluting concentrated acids and bases add the acid or base to water

27. Example 1
How many milliliters of 3.0M H2SO4 are needed to make 450 mL of .10M H2SO4?