Aqueous AcidBase Equilibria - PowerPoint PPT Presentation

1 / 39
About This Presentation
Title:

Aqueous AcidBase Equilibria

Description:

Solvolysis. Autoionization of Water. ion product of water, Kw. pH and pOH. Strong Electrolytes. Strong electrolytes dissociate completely in aqueous solutions ... – PowerPoint PPT presentation

Number of Views:164
Avg rating:3.0/5.0
Slides: 40
Provided by: charle407
Category:

less

Transcript and Presenter's Notes

Title: Aqueous AcidBase Equilibria


1
  • Aqueous Acid-Base Equilibria

2
Keywords Concepts
  • Electrolytes
  • Autoionization of Water
  • ion product of water, Kw
  • pH and pOH
  • Ionization Constants for Weak Acids and Bases,
  • Ka (pKa) Kb (pKb)
  • Polyprotic Acids
  • Solvolysis

3
Strong Electrolytes
  • Strong electrolytes dissociate completely in
    aqueous solutions
  • Weak electrolytes dissociate partially
  • Nonelectrolytes do not dissociate
  • Three classes of strong electrolytes
  • Strong Acids

4
What is H (aq)?

H3O
H
H5O2
H9O4
5
Representing Protons
  • All representations of the proton are equivalent.
  • H5O2 (aq), H7O3 (aq), H9O4 (aq) have been
    observed.
  • We will use H(aq) most of the time!

6
Acid-base Properties
Bronsted Lowry Theory ACID A proton
donor BASE A proton acceptor
-COOH -OH -NH2 HCl
NH3 OH- -COO-
NH3 H2O ? NH3 OH-
Bronsted Base Acid

Conjugate Acid
Base
7
Ephedrine hydrochloride
Ephedrine
Base and Conjugate Acid
Base Ephedrine
Conjugate acid The product resulting from the
addition or acquisition of a proton.
8
Strong Electrolytes
  • Strong Bases

9
Strong Electrolytes
  • Soluble Salts

10
Strong Electrolytes
  • Calculation of concentrations of ions in solution
    of strong electrolytes is easy
  • Calculate the concentrations of each ion in 0.050
    M nitric acid, HNO3.

11
Strong Electrolytes
  • Calculate the concentrations of each ion in 0.020
    M calcium hydroxide, Ca(OH)2, solution.

12
The Auto-Ionization of Water
  • Pure water dissociates very slightly
  • less than one-millionth molar

13
The Auto-Ionization of Water
  • Because the activity of pure water is 1, the
    equilibrium constant for this reaction is

14
The Auto-Ionization of Water
  • Experimental measurements have determined that
    the concentration of each ion is 1.0 x 10-7 M at
    250C

15
The Auto-Ionization of Water
  • This particular equilibrium constant is called
    the ion-product for water, Kw.

16
The Auto-Ionization of Water
  • Calculate the concentrations of H3O and OH- in
    0.050 M HCl.

17
The Auto-Ionization of Water
18
The Auto-Ionization of Water
  • Increase in H3O from HCl shifts the
    equilibrium and decreases the OH-.
  • A concentration of 2.0?10-13 M is difficult to
    visualize.

19
The pH and pOH scales
  • A convenient way to express acidity and basicity
  • pH is defined as

20
The pH and pOH scales
  • In general, a lower case p before a symbol is
    read as negative logarithm of the symbol

21
The pH and pOH scales
  • If we know either H3O or OH-, then we can
    calculate pH and pOH.
  • Calculate the pH of a solution in which the
    H3O 0.030M.

22
The pH and pOH scales
  • The pH of a solution is 4.597. What is the
    concentration of H3O?

23
The pH and pOH scales
  • A convenient relationship between pH and pOH may
    be derived for all dilute aqueous solutions at
    25C.

24
The pH and pOH scales
  • Taking the logarithm of both sides of this
    equation gives
  • Multiplying both sides of this equation by -1
    gives

25
The pH and pOH scales
  • Or, in a slightly different form, we have

Remember these two equations!!
26
The pH and pOH scales
  • The typical (practical) range for the pH scale is
  • and for pOH the scale is

27
The pH and pOH scales
  • Calculate H3O, pH, OH-, and pOH for
  • 0.020 M HNO3 solution.

You do it!
28
The pH and pOH scales
  • Calculate H3O, pH, OH-, and pOH for 0.020 M
    HNO3 solution.

You do it!
29
(No Transcript)
30
Ionization Constants for Weak Monoprotic Acids
and Bases
  • Consider the dissolution of acetic acid, a weak
    acid, in water as an example.
  • The equation for the ionization of acetic acid is

31
(No Transcript)
32
Ionization Constants for Weak Monoprotic Acids
and Bases
  • The equilibrium constant for this ionization is
    expressed as

33
Ionization Constants for Weak Monoprotic Acids
and Bases
  • There is a specific equilibrium constant symbol
    for the ionization of an acid
  • Ka acid ionization constant

34
(No Transcript)
35
Ionization Constants for Weak Monoprotic Acids
and Bases
  • Values for several ionization constants

36
(No Transcript)
37
Ionization Constants for Weak Monoprotic Acids
and Bases
  • From the above table we see that the order of
    increasing acid strength for these weak acids is

38
Ionization Constants for Weak Monoprotic Acids
and Bases
  • The order of increasing base strength of the
    anions (conjugate bases) of these acids is

39
Ionization Constants for Weak Monoprotic Acids
and Bases
  • Write the equation for the ionization of the weak
    acid HCN and the expression for its ionization
    constant.

You do it!
Write a Comment
User Comments (0)
About PowerShow.com