Transcript Bell Ringer

Bell Ringer
pH
1-6
7
Solution
Added
Litmus paper
changes from
Acid
Neutral
Blue to
Red
Does not
Change
8-14
Base
Red to
Blue
Which of the following aqueous solutions will cause litmus
paper to turn red?
A NaOH
B NaCl
C HCl
D H2O
Source: 2003 VA EOC Exam
pH
Ms. Besal
4/14/2006
A Quick Reminder…
• Reactions can stop at an EQUILIBRIUM
NO2 + NO2
N 2O 4
Image source: http://cwx.prenhall.com
The Equilibrium Constant, Keq
For the reaction:
aA + bB
cC + dD
Where:
• a, b, c, d are coefficients
• A, B, C, D are substances
Keq =
[C]c [D]d
(products)
[A]a [B]b
(reactants)
[ ] = concentration in M
The Equilibrium Constant, Keq
For the reaction:
NO2 + NO2
Keq =
N 2O 4
[N2O4]1
=
1
1
[NO2] [NO2]
2 NO2
Keq =
[N2O4]1
[NO2]2
[N2O4]
[NO2]2
N 2O 4
=
[N2O4]
[NO2]2
A Special Equilibrium Constant, Kw
For the reaction:
H2O + H2O
Kw =
[H3O+] [OH-]
[H2O]2
H3O+ + OH-
+] [OH-]
[H
O
=
3
“hydronium” “hydroxide”
-7] [1.00 x 10-7] = 1.00 x 10-14
[1.00
x
10
Kw =
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Practice Problems
Using the knowledge that Kw = 1.00 x 10-14, solve for
the missing piece of information:
1. Calculate the hydroxide ion concentration in a solution whose
hydronium ion concentration is 1 x 10-5 M
Kw = [H3O+] [OH-]
1.00 x 10-14 = [1 x 10-5 M] [OH-]
[OH-] = 1.00 x 10-14
1 x 10-5 M
=
1 x 10-9 M
Practice Problems
2. Calculate the hydronium concentration for a solution whose
hydroxide concentration is 0.0010 M.
Kw = [H3O+] [OH-]
1.00 x 10-14 = [H3O+] [0.0010 M]
[H3O+] = 1.00 x 10-14 =
0.0010 M
1 x 10-11 M
Practice Problems
3. What is the hydroxide concentration of a solution if 0.080
grams of NaOH are dissolved in 2.0 L of solution? 0.0010 M OHWhat is the hydronium ion concentration of this solution?
1.0 x 10-11 M H3O+
0.080 g NaOH x 1 mol NaOH x
40.00 g NaOH
[OH-] =
1 mol OH= 0.0020 mol OH
1 mol NaOH
0.0020 mol OH2.0 L
Kw = [H3O+] [OH-]
= 0.0010 M OH-
1.00 x 10-14 = [H3O+] [0.0010 M]
[H3O+] = 1.00 x 10-14
= 1.0 x 10-11 M H3O+
0.0010 M
Practice Problems
4. What is the hydroxide ion concentration of a solution if 0.080
grams of Ca(OH)2 are dissolved in 2.0 L of solution? 0.0020 M OHWhat is the hydronium ion concentration of this solution?
9.3 x 10-12 M H3O+
1
mol
Ca(OH)
2
mol
OH
2 x
0.080 g Ca(OH)2 x
= 0.00216 mol
74.10 g Ca(OH)2 1 mol Ca(OH)2 OH-
[OH-] =
0.00216 mol OH- = 0.00108 M OH2.0 L
Kw = [H3O+] [OH-]
1.00 x 10-14 = [H3O+] [0.00108 M]
[H3O+] = 1.00 x 10-14
= 9.3 x 10-12 M H3O+
0.00108 M
pH – the POWER of H+!
These numbers represent the POWER of H+
pH = the negative logarithm of [H3O+]
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Log-o-rhythms
=
=
pH – the POWER of H+!
pH = the negative logarithm
POWER of [H3O+]
pH = - log [H3O+]
Answer the following questions without using a calculator:
• What is the pH of a solution with [H3O+] = 1.0 x 10-4 M?
pH = 4.00 ACID
• What is the pH of a solution with [H3O+] = 1.0 x 10-12 M?
pH = 12.00 BASE
My Kingdom for a Calculator!
To solve for pH, given hydronium molarity
On TI-83:
On Scientific Calculators:
• push “(-)” key
• type in number
• push “log” key
• push “log” key
• type in number
• push +/- key
Practice Problems
1. What is the pH of a solution if the concentration of
hydronium ions is 1.0 x 10-2 M? Is the solution acidic or basic?
pH = - log [H3O+]
pH = - log (1.0 x 10-2)
pH = 2.00 ACIDIC
SIG FIG RULES:
Put the correct number of Sig Figs
BEHIND the decimal point.
Practice Problems
2. What is the pH of a solution if the concentration of
hydroxide ions is 1.0 x 10-4 M? Is the solution acidic or basic?
Kw = [H3O+] [OH-]
1.00 x 10-14 = [H3O+] [1.0 x 10-4 M]
[H3O+] = 1.00 x 10-14 =
1.0 x 10-4 M
pH = - log [H3O+]
pH = - log (1.0 x 10-10)
pH = 10.00
BASIC
1 x 10-10 M
My Kingdom for a Calculator (again)!
To solve for hydronium molarity, given pH
On TI-83:
On Scientific Calculators:
• push “10x” key
• type in number
• push “(-)” key
• push +/- key
• type in pH
• push “2nd” key
• push “log” key
Practice Problems
3. What is the concentration of hydronium ions in a solution
whose pH is 8.00?
pH = 8.00 = - log [H3O+]
-8.00 = log [H3O+]
10–8.00 M = [H3O+]
[H3O+] = 1.00 x 10-8 M
Practice Problems
4. For Question #3, what is the concentration of hydroxide ions?
Kw = [H3O+] [OH-]
1.00 x 10-14 = [1.0 x 10-8 M] [OH-]
[OH-] =
1.00 x 10-14 =
1.0 x 10-8 M
1 x 10-6 M
Practice Problems
5. What is the concentration of hydronium ions in a solution
that has a volume of 2.50 L and 5.33 g of HCl? What is the pH
of this solution?
5.33 g HCl x
[H+] =
1 mol HCl x
36.46 g HCl
0.146 mol H+
2.50 L
pH = - log [H3O+]
pH = - log (0.0584)
pH = 1.234
1 mol H+
1 mol HCl
+
= 0.146 mol H
= 0.0584 M H+