1. Solutions, Acids, and Bases
Chapter 8
Solutions, Acids, and Bases

2. Sec. 8.1, Formation of Solutions
Solutions are homogeneous mixtures of two or more substances.
Remember, homogeneous mixtures have equal distribution of the different substances.
Substances in homogenous mixtures can be any form of matter, to include elements, compounds, or ions.
These substances can also be solid, liquid, or gas.

3. Sec. 8.1, Formation of Solutions
All mixtures are made up of 2 parts, the solute and the solvent.
The solute is the part of the solution whose particles are being dissolved.
The solvent is the substance in which the solute is dissolved.

5. Sec. 8.1, Formation of Solutions
Of the different solutions listed, Solutions with H2O as the solvent are the most common.
Many scientists refer to water as “the universal solvent” , because so many things dissolve in it.
Because the H2O molecule is polar, it is able to dissolve many substances.

6. Sec. 8.1, Formation of Solutions
Substances dissolve in water in three ways.
Dissociation
Dispersion
Ionization

7. Sec. 8.1, Formation of Solutions
Dissociation of Ionic Compounds
Solvent and solute particles must attract one another
With ionic solutes, the cations are attracted to the (-) end of the polar water molecule and anions are attracted to its positive end.

8. Notice how the polar water molecules pull the Na+ and Cl- ions out of the NaCl crystal and hydrate (surround) them, thus dissolving them and keeping them in solution.

9. Sec. 8.1, Formation of Solutions
Dispersion of Molecular Compounds
In this situation if the solvent and solute are both made of polar molecules, they will attract each other.
This is done on a molecular level.
The molecules remain intact and nothing is ionized or reacts.
As molecules of solvent and solute attract, they are dispersed throughout the solution.
Example: Sugar dissolving in water.

10. Notice the even dispersion of the sugar molecules in water on the left and how SiO2 (sand) separates from water on the right.

11. Sec. 8.1, Formation of Solutions
Remember for dispersion of molecular compounds, both solvent and solute must be made of polar molecules!
polar and non polar molecules will not mix.
2 non-polar molecules will not mix.

12. Sec. 8.1, Formation of Solutions
Ionization of Molecular Compounds
In this process, molecular compounds react to form two ions.
Ionization of HCl gas in H2O
HCl gas is added to H2O and two ions form
The Cl- ion (chloride ion)
The H3O+ ion (hydronium ion)
HCL + H2O H3O+ + Cl-

13. Ionization of HCl, forming a hydronium (H3O+) ion.

14. Sec. 8.1, Formation of Solutions
Ionization of HCl and H2O (continued)
Notice, the neutral compounds H20 and HCl gain or loose electrons in the ionization process.
The ions pulled into solution are formed by a chemical reaction that ionizes the particles of the solvent and solute.

16. Sec. 8.1, Formation of Solutions
Properties of Liquid Solutions
When a solute and solvent combine to form a solution, physical properties of both solute and solvent change.
Three physical properties that change:
Conductivity
Freezing Point
Boiling Point

17. Sec. 8.1, Formation of Solutions
Conductivity
Solid NaCl is a poor conductor of electricity, however, when it is dissolved in H2O, it becomes an excellent conductor.
Gaseous HCl is a poor conductor until it is mixed with H2O, then it becomes a good conductor of electricity
Ionized particles in solution are good conductors.

18. Sec. 8.1, Formation of Solutions
Freezing Point
When a solute MgCl2 is mixed with the solvent H2O, the Mg2+ and Cl- ions that form prevent the water from forming crystals and freezing.
The same thing happens when you add antifreeze (ethylene glycol) to your car to keep the engine from freezing.
Addition of a solute inhibits a solvent’s ability to crystallize and freeze.

19. Notice the diagram to the left of pure water crystallizing (freezing)
Notice the diagram to the left of pure water crystallizing (freezing). Notice how the introducing of Mg2+ and Cl- ions to the water prevent crystals from forming.

20. Sec. 8.1, Formation of Solutions
Boiling Point
Adding a solute to a solvent will cause the boiling point of the solution they form to be raised.
Ethylene glycol (antifreeze) can raise the boiling point of water
Ethylene glycol also lowers the freezing point of water.

21. Sec. 8.1, Formation of Solutions
Heat of Formation
During the formation of a solution, energy is either released or absorbed.
Like in chemical reactions, heat of formation is described as either being exothermic or endothermic.

22. Sec. 8.1 Formation of Solutions
Factors Affecting Rates of Dissolving
Like in chemical reactions, collisions have a lot to do with how fast a substance dissolves.
The more collisions, the faster solutes dissolve
The three main factors are;
Surface area
Stirring
Temperature

23. Section 8.1, Quiz
1. Solutions are _________ mixtures of 2 or more substances.
2. A solution is composed of a ______ and a _________.
3. The particles of the _________ are dissolved in the ________.
4. Water is often referred to as the _________ ________ by scientists.

24. Section 8.1 Quiz
5. The reason so many things dissolve in H2O is that the H2O molecule is _______.
6. Name the three ways that substances dissolve in H2O.
7. A polar solvent (will/will not) form a solution with a non polar solute.

25. Sec. 8.2, Solubility & concentration
Solubility is the amount of solute that can be dissolved in a given amount of solvent at a constant temperature and pressure.
Example: 36 grams of table salt can be dissolved in 100 grams of H2O at a temperature of 20oC
Different compounds and elements have different solubilities

27. Sec. 8.2, Solubility & concentration
Saturated
A solution is said to be saturated if it contains all of the solute that the solvent can hold
Unsaturated
In an unsaturated solution the solvent can hold more solute.

28. Sec. 8.2, Solubility & concentration
Solubility (continued)
Supersaturated
Supersaturated solutions contain more solute than a solution can normally hold at a given temperature
Example: Sugar in sweet tea.

29. Sec. 8.2, Solubility & concentration
There are three factors that affect solubility.
Polar and non polar solvents
The general rule is “like dissolves like.
Polar solutes tend to dissolve in polar solvents.
Non-polar solutes tend to dissolve in non polar solvents
Notice chart on next page.

31. Sec. 8.2, Solubility & concentration
Factors Affecting Solubility (cont.)
Temperature
Gases tend to become less soluble in water as they become warmer.
Example: CO2 in a soda
Solids tend to become more soluble in water as temperature increases.
Example: Sugar in tea

32. Notice how the solubility of potassium nitrate (a solid) increases as the water temperature increases.

33. Notice that the trend of solubility increasing with temperature holds true with these other compounds as well.

34. Sec. 8.2, Solubility & concentration
Pressure
Gases can be forced into solution by putting them under pressure in the presence of a solvent.
The carbonation of a soda is simply CO2 gas being forced into the liquid soda under pressure.

35. Factors Affecting Solubility
Pressure
Temperature
Polar and Non-Polar Solvents

36. Sec. 8.2, Solubility & concentration
There are three Ways to state the concentration of a solution
Percent by volume
% by Volume = Volume of solute X 100%
Volume of Solution
Remember, the volume of the solution = the volume of the solvent + the volume of the solute.

37. Sec. 8.2, Solubility & concentration
Percent by Mass
% by Mass = Mass of Solute X 100%
Mass of Solution
* It is important to remember that the mass of solution is the sum of the mass of the solvent + the mass of the solvent

38. Sec. 8.2, Solubility & concentration
Molarity
Molarity = Moles of solute
Liters of solution
Molartiy is usually expressed in moles per liter or mol/l

39. Sec. 8.2, Solubility & concentration
Ways To Express Concentration of a Solution.
Concentration
% by volume
% by mass
Moles

40. Section 8.2 Quiz
1. The amount of solute that can be dissolved in a given amount of solvent at a constant temperature is called ____________.
2. A solution in which the solvent contains all of the solute that it can hold is said to be a _______ solution.

41. Section 8.2 Quiz
3. A solution in which more solute can be dissolved in the solute is called a _________ solution.
4. A solution which contains more solute than it normally would hold at a given temperature is called a ______ __________ solution.

42. Section 8.2 Quiz
5. The three factors that affect solubility are: _________________, ___________, and ______________.
6. The three ways we express the concentration of a solution are: ___________, ______________, and _________________.

43. Sec. 8.3, Properties of Acids and Bases
Identifying Acids
Acids are compounds that produce hydronium ions H3O+.
HCl + H2O H3O+ + Cl-.
Hydrogen chloride gas dissolved in water yields hydronium ion + the chloride ion. The solution is Hydrochloric Acid.

44. Sec. 8.3, Properties of Acids and Bases
Identifying Acids
General properties of acids include:
1. A sour taste
2. Reactivity with metals
3. The ability to produce color change with indicators

45. Sec. 8.3, Properties of Acids and Bases
Sour Taste
This characteristic associated with acids is pretty accurate, but not advisable to be used in a laboratory setting.
Lemons and grapefruits have a sour taste due to the acetic acid (CH3COOH) they contain.
Sour milk contains butyric acid, which has a very sour taste.

46. Sec. 8.3, Properties of Acids and Bases
Reactivity With Metals
Acids react readily with most metals they come in contact with.
Zinc (Zn) and hydrochloric acid (HCl) react readily to form ZnCl Zn + 2HCl ZnCl2 + H2.
It is important to understand that all acids will not react with all metals and those that do react, react to different degrees.

47. Sec. 8.3, Properties of Acids and Bases
Color Changes in Indicators
We use color change in certain indicators like the ones listed below to identify acids.
Blue Litmus Paper – Turns red in acid
Phenolthalene – Turns red in acid

48. Testing For Acidity Using Litmus Paper

50. Sec. 8.3, Properties of Acids and Bases
Identifying Bases
General Properties of Bases
Bitter to the taste
Slippery feel
Produce changes in indicators

51. Sec. 8.3, Properties of Acids and Bases
Color Change in Indicators
Changes Red Litmus Paper to Blue
Changes Phenolthalien to Red
Slippery Feel
Wet Soap
Cleaning Products
Bitter Taste
Baking Chocolate
Unflavored Cough Syrup

52. Sec. 8.3, Properties of Acids and Bases
General information about acids and bases
Acids can be defined as proton donors.
Acids produce the hydronium ion (H3O+)
Bases can be defined as proton acceptors.
Bases produce the polyatomic ion called the hydroxide ion (OH-)

53. Sec. 8.3, Properties of Acids and Bases
Neutralization Reaction
Occurs when an acid and a base are combined.
In this reaction, the products are a salt and water.
HCl + NaOH NaCl + H2O
(acid) (base) (salt) (water)

54. Sec. 8.3, Properties of Acids and Bases

55. Sec. 8.3, Properties of Acids and Bases
Electrolytes

56. Sec. 8.4, Strength of Acids and Bases
The pH Scale
The pH scale is the scale we use to measure the strength of acids and bases.
It is numbered 1-14
1 would represent the strongest acid
14 would represent the strongest base
7 is neutral, neither acid nor base.
Acids are less than 7
Bases are greater than 7

57. Sec. 8.4, Strength of Acids and Bases
The pH Scale
pH is based on the hydronium ion concentration (H3O+) of a solution.
The lower the pH value, the higher the H3O+ concentration of the solution.
The higher the H3O+ concentration, the more acidic the solution is.
The higher the pH value the lower the H3O+ concentration is, so the solution is more basic.

58. pH Values of Some Common Items

60. Sec. 8.4, Strength of Acids and Bases
Strong Acids and Bases
Strong Acids
Ionize almost completely when they dissolve in H2O.
HCl, H2SO4 and HNO3 are strong acids.
Strong Bases
Dissociate almost completely in H2O.
NaOH, Ca(OH)2 and KOH are strong bases.

61. Sec. 8.4, Strength of Acids and Bases
Weak Acids and Bases
Weak Acids
Forms fewer H3O+ ions than strong acid.
Dissociate only slightly in H2O.
Has higher pH # than a strong acid.
Weak Bases
Forms fewer OH- ions than strong base.
Dissociates only slightly in H2O.
Has lower pH # than strong base.

62. Sec. 8.4, Strength of Acids and Bases
Buffers
Buffers are substances that are resistant to large changes in pH.
It can react with either an acid or a base
Buffers are prepared by mixing a weak acid and its salt or a weak base and its salt.

63. Sec. 8.4, Strength of Acids and Bases
Electrolytes
Electrolytes are substances that ionize or dissociate into ions when dissolved in water.
Electrolytes can conduct an electric current.
Strong acids and strong bases are strong electrolytes because they ionize almost completely in H2O.

64. Section 8.4 Quiz
1. The measure of a substance’s acidity or bacisity is called its _____.
Acids are considered to be proton _________, while bases are considered to be proton ________.
A substance with a pH of 7 would be considered to be __________.

65. Section 8.4 Quiz
4. A substance with a pH of 13 would be considered to be a ________.
5. A substance with a pH of 3 would be considered to be a ________
6. pH is based on the _________ concentration of a solution.

66. Section 8.4 Quiz
7. _____________ are substances which ionize or dissociate when added to water.
8. Bases are substances which form ________ ions while acids form ________ions.