Solutions, Acids, Bases, and Salts

1
Solutions, Acids, Bases, and Salts
2
The Nature of Solutions

• Solution homogenous mixture of 2 or more
  substances in single physical state.
• Properties of Solutions
• Solute substance that dissolved
• Solvent substance that does the dissolving
• Example salt water salt is the solute, water is
  the solvent

3

• Soluble substance that dissolves in another
  substance capable of being dissolved
• Insoluble substance that does not dissolve in
  another substance

4

• Types of Solutions
• Solid solution most contain 2 or more metals
• Alloys
• Formed by melting component metals, mixing them
  together, and cooling
• Example
• sterling silver silver with small amount of
  copper
• gold for jewelry gold and copper

5
(No Transcript)
6

• Gaseous Solution 2 or more gases are mixed
• Liquid solution solute may be a gas, liquid, or
  a solid, but solvent is a liquid
• Example
• Vinegar acetic acid dissolved in water
• Antifreeze ethylene glycol dissolved in
  water
• Soft drinks carbon dioxide dissolved in
  water
• Aqueous solution solutions with water as
  solvent

7
(No Transcript)
8
Concentration of Solutions

• Concentration amount of solute in given amount
  of solvent or solution
• Molarity M - of moles of solute dissolved in
  each liter of solution
• M moles solute
• liter solution

9

• What is the molarity if 10.0 g of NaOH is
  dissolved in 0.100 L of water?

10

• Molality m - number of moles of solute
  dissolved in each kilogram of solvent
• m moles solute
• Kg solvent

11

• What is the molality of a solution made from 18.0
  g C6H12O6 dissolved in 1.00 kg of water?

12

• Saturation solution contains as much solute as
  can possibly be dissolved under the existing
  conditions of temperature and pressure

13
(No Transcript)
14

• Unsaturated solution that has less than maximum
  amount of solute that can be dissolved

15

• Supersaturated solution that contains greater
  amount of solute than is needed to form saturated
  solution.

16
(No Transcript)
17
The Formation of Solutions

• Solvation interaction between solute and
  solvent particles
• Hydration solvation when solvent is water

18
(No Transcript)
19

• Solubility amount of solute that will dissolve
  in specific solvent under given conditions

20

• Factors influencing solubility
• Nature of solute or solvent
• Polar or nonpolar like dissolves like
• Polar will dissolve polar
• Nonpolar will dissolve nonpolar

21

• Temperature
• Gas in liquid solutions solubility decreases
  with increasing temperature
• Solid in liquid solution solubility increases
  with increasing temperature

22
(No Transcript)
23
(No Transcript)
24

• Pressure
• Gas in liquid solution solubility increases
  with increasing pressure

25
(No Transcript)
26
The carbon dioxide concentration was high due to
the high pressure deep in the lake High pressure
increases the solubility of carbon dioxide in
water.
Lake Nyos in Cameroon was the site of a natural
disaster, in which a concentrated solution of
carbon dioxide in water suddenly released enough
carbon dioxide gas to suffocate 1700 people.
27
Defining Acids and Bases

• Properties of Acids and Bases
• Taste
• Acids
• Sour
• Citrus fruits citric acid
• Yogurt and sour milk lactic acid
• Soda carbonic acid and phosphoric acid
• Vinegar acetic acid

28

• Bases
• Bitter
• Soap!
• Oops! NEVER taste anything in the lab!

29

• Touch
• Acids
• Dilute acids feel like water
• Stronger acids burn or sting
• Bases
• Mild bases only sting eyes, otherwise smooth,
  soothing or slippery
• Strong bases burn or sting, slippery

30

• Reactions with metals
• Acids react vigorously with any metals
• Bases do not react with most metals

31

• Electrical Conductivity
• Acids conduct as a solution
• Bases conduct as a solution
• Both are electrolytes substances that dissolve
  and become ionized.

32

• Indicators
• Litmus made from a species of lichen
• Acid turns litmus paper from blue to red, or
  doesnt change red paper
• Base turns litmus paper from red to blue, or
  doesnt change blue paper
• Phenolphthalein
• Methyl red
• Thymol blue

33
(No Transcript)
34

• Neutralization properties of both acid and base
  are neutralized when proper amounts of each are
  mixed together.
• The solution becomes neutral
• Acid-base neutralization reaction
• HX YOH ? HOH YX
• water salt
• Salt - crystalline compounds that have high
  melting point, are good electrolytes, and are
  conductors of electricity

35
(No Transcript)
36

• Arrhenius Definition
• Acid substance that dissociates in water to
  produce H ions
• Base substance that dissociates in water to
  produce OH- ions

37

• Easier to use to show how acid/base reactions
  neutralize each other
• H(aq) OH-(aq) ? HOH(l)
• HCl(aq) NaOH(aq) ? HOH(l) NaCl(aq)

38
(No Transcript)
39

• Bronsted-Lowry Definition
• Acid any substance that can donate H ions
• Base any substance that can accept H ions
• Different than the Arrhenius, such that
• Acids and bases defined independently of water
• Focuses solely on H ions

40
(No Transcript)
41

• Three types of acids
• Monoprotic donate one proton, H
• HCl
• HNO3
• HC2H3O2
• Diprotic donate two protons
• H2SO4
• H2CO3
• Triprotic donate three protons
• H3PO4

42

• Hydronium ion, H3O a proton, H, is attracted
  to the negative electrons surrounding water
• H H2O ? H3O
• HCl(g) H2O(l) ? H3O(aq) Cl- (aq)
• This is more correct than to write
• HCl H2O ? H Cl-
• This way does not show who is the proton donor or
  acceptor

43
(No Transcript)
44

• In the reaction
• NH3(g) H2O(l) ? NH4(aq) OH-(aq)
• What is the proton donor and acceptor?

45

• Water is considered to be amphoteric, it can act
  as an acid or as a base!

46

• Conjugate Acid-Base Pairs
• Conjugate acid the base that accepts a H
• Conjugate base the acid that loses a H
• NH3 (g) H2O (l) NH4 (aq) OH- (aq)
• base acid conjugate conjugate
• acid
  base

47

• HCl (aq) H2O (l) H3O (aq) Cl- (aq)
• acid base conjugate conjugate
• acid
  base

48
Determining Strengths of Acids and Bases

• Some acids are much stronger than other acids
• Some bases are much stronger than other bases

49

• Strong and Weak Acids
• Strong Acids readily transfer H ions to water
  to form H3O ions
• They are strong electrolytes
• Weak Acids dont readily transfer H ions to
  water
• They are poor electrolytes

50
(No Transcript)
51

• Strong and Weak Bases
• Strong Base have a strong affinity for H ions
• OH- is a strong base, so they attract H ions
• Weak Base react partially with water to form
  OH- ions

52
(No Transcript)
53

• Strength of Conjugate Acid-Base Pairs
• The stronger the acid, the weaker the conjugate
  base
• The stronger the base, the weaker the conjugate
  acid

54

• Ka Acid dissociation constant method of
  quantifying the strength of an acid
• HA (aq) H2O (l) H3O (aq) A- (aq)
• If Keq H3OA-
• HA
• Then Ka H3OA-
• HA

55

• The larger the Ka, the more acid reacts with H2O
  to produce H3O
• The greater the Ka, the stronger the acid
• All acids have a characteristic Ka value
• Weak acids have Kalt1
• Strong acids have Kagt1

56

• Kb Base dissociation constant measure of the
  strength of a base
• B (aq) H2O (l) HB (aq) OH- (aq)
• Kb HBOH-
• B
• Weak bases have Kblt1
• Strong bases have Kbgt1

57

• Aspirin, acetylsalicylic acid, is a weak
  monoprotic acid. A chemist mixes 0.1000 mole of
  aspirin in 1.000L of H2O. When the solution
  reaches equilibrium, she measures the
  concentration of H3O to be 0.0057 M. Calculate
  the Ka for aspirin.
• HA H2O H3O A-
• Ka H3OA-
• HA

58

• HA H2O H3O A-
• Initial 0.1000M 0
  0
• Change -0.0057M 0.0057M
  0.0057M
• Equilibrium 0.0943M 0.0057M
  0.0057M
• Ka H3OA- (0.0057)(0.0057)
• HA (0.0943)
  
  3.4 x 10-4
• Kalt1, therefore aspirin is a weak acid

59

• Acid-Base Properties of Salts
• Salts are strong electrolytes
• The ions formed from dissociation in water can be
  weak Bronsted-Lowry acids or bases
• Salts of strong acids/bases solutions are
  neither acidic nor basic, they are neutral
• NaOH(aq) HCl(aq) ? NaCl(aq) H2O(l)

60

• Salts of strong acid and weak base solutions
  are acidic
• NH3(aq) HCl(aq) ? NH4Cl(aq)
• Weak base strong acid Bronsted-Lowry
  acid(slightly acidic)
• Salts of weak acid and strong base solutions
  are basic
• 2NaOH(aq) H2CO3(aq) ? Na2CO3(aq)
  2H2O(l)
• Strong base weak acid weak
  Bronsted-Lowry base(slightly
  basic)

61

• Salts of weak acid/base solutions can be
  acidic, basic, or neutral, depending on relative
  strengths of acids/bases from which salt is formed