2. Complete the
Teaching Idea “Concept Questions for Chemistry using PhET” posted by Trish
Loeblein on the pH Scale simulation at PHET (http://phet.colorado.edu/en/simulation/ph-scale). On your
blog post the answers with your scientific explanations from the “Clicker
Questions pH Scale” posted by Trish.
1. The Color of a
solution identifies if it is an acid, base, or neutral solution?
B.
False
2. Which solution
is basic?
D.
More than one
3. Which Solution
is acidic?
C.
4. Which solution
is basic?
B.
5. Which solution
is basic?
B.
6. How will adding
water affect the pH?
A. The more water lessens the
acidity, so the pH goes up
7. How will equal
amount of water affect the pH?
B. more water lessens the basicity,
so pH goes down, but not by 2
8. What is the
order from more acidic to most basic?
A. ABC-the most acidic has the
lowest pH and as it increases it becomes more basic
9. What is the order
from most acidic to most basic?
C-BAC-the most acidic will have a
larger quantity of H3O+ and the neutral will have equal parts the base will
have less
10. If spit has
pH=7.4, what does that tell you about the water equilibrium?
Since the pH is not 7, then
something must have been added to force the equilibrium shift to the left.
3. Complete the Teaching Idea “Intro to Strong and Weak Acids and Bases” posted by Chris Bires on the Acid-Base Solutions simulation (http://phet.colorado.edu/en/simulation/acid-base-solutions) and post on your blog your data and answers to the questions posed.
·
Begin
with a strong acid and lower the pH
probe into the beaker. What is the pH of
this solution?
·
Test
this strong acid with both pH paper and the conductivity probe. What color does the pH indicator become? Is this strong acid an electrolyte? Does current travel through this solution?
·
Repeat
the above tests with the weak acid, the strong base, and the weak base, and
water. Collect your observations in the
table below:
|
|
Strong Acid
|
Weak Acid
|
Strong Base
|
Weak Base
|
Water
|
|
pH meter read
(value)
|
2.0
|
4.5
|
12.00
|
9.50
|
7
|
|
pH paper
(color)
|
Red (2)
|
Orange (4)
|
Blue (12)
|
Green (9)
|
Yellow (7)
|
|
Conductivity
(bright/dim/none)
|
bright
|
dim
|
bright
|
dim
|
none
|
|
Exists as Mostly
(ions/molecules)
|
Molecules
|
Molecules
|
Both
|
Ions
|
molecules
|
Procedure: 
This simulation allows you to
change the concentration of a strong and weak acid and base.
Complete the table below for
some strong acids and bases and weak acids and bases by adjusting the
concentration.
Strong Acids
|
Strength
|
Initial Acid Concentration (mol/L)
|
[HA] (mol/L)
|
[A-] (mol/L)
|
[H+] (mol/L)
|
pH
|
 |
.010 M
|
Negligible
|
1.03 X 10^-2
|
1.03 X 10^-2
|
1.99
|
|
|
.050 M
|
Negligible
|
4.95 X 10^-2
|
4.95 X 10^-2
|
1.31
|
|
|
.100 M
|
Negligible
|
1.00 X 10^-1
|
1.00 X 10^-1
|
1
|
|
|
1.00 M
|
1.00 X 10^1
|
3.16 X 10^-4
|
3.16 X 10^-4
|
3.50
|
Weak Acids
|
Strength (approximately)
|
Initial Acid Concentration (mol/L)
|
[HA] (mol/L)
|
[A-] (mol/L)
|
[H+] (mol/L)
|
pH
|
 |
.015 M
|
1.50 X 10^-2
|
1.96 X 10^-6
|
1.96 X 10^-6
|
5.71
|
|
|
.150 M
|
1.50 X 10^-1
|
1.22 X 10^-4
|
1.22 X 10^-4
|
3.91
|
 |
.015 M
|
1.30 X 10^-2
|
1.98 X 10^-3
|
1.98 X 10^-3
|
2.70
|
|
|
.150 M
|
2.24 X 10^-4
|
1.50 X 10^-1
|
1.50 X 10^-1
|
.082
|
Strong Bases
|
Strength
|
Initial Acid Concentration (mol/L)
|
[MOH] (mol/L)
|
[M+] (mol/L)
|
[OH-] (mol/L)
|
pH
|
|
|
.010 M
|
Negligible
|
1.00 X 10^-2
|
1.00 X 10^-2
|
12.0
|
|
|
.050 M
|
Negligible
|
5.00 X 10^-2
|
5.00 X 10^-2
|
12.7
|
|
|
.100 M
|
Negligible
|
1.00 X 10^-1
|
1.00 X 10^-1
|
13.0
|
|
|
1.00 M
|
Negligible
|
1.00 X 10 ^ 0
|
1.00 X 10 ^ 0
|
14.0
|
Weak Bases
|
Strength (approximately)
|
Initial Acid Concentration (mol/L)
|
[B] (mol/L)
|
[BH+] (mol/L)
|
[OH-] (mol/L)
|
pH
|
|
|
.015 M
|
1.50 X 10^-1
|
7.18 X 10^-6
|
7.18 X 10^-6
|
8.86
|
|
|
.150 M
|
1.50 X 10^-2
|
2.68 X 10^-5
|
2.68 X 10^-5
|
9.43
|
|
|
.015 M
|
2.26 X 10^-6
|
1.50 X 10^-2
|
1.50 X 10^-2
|
12.18
|
|
|
.150 M
|
2.24 X 10^-4
|
1.50 X 10^-1
|
1.50 X 10^-1
|
13.18
|
Conclusion
Questions:
1.
A
strong acid is very concentrated / exists primarily as ions.
(circle)
2.
A
weak base is a nonelectrolyte / weak
electrolyte / strong
electrolyte.
3.
A
strong base is a nonelectrolyte / weak electrolyte / strong
electrolyte.
4.
At
the same concentration (Molarity) a strong acid will have a higher / lower / the same pH as a weak acid.
5.
As
concentration of a weak acid increases, the pH increases / decreases
/ remains constant.
6.
As
concentration of a weak base increases, the pH increases /
decreases / remains constant.
7.
As
the concentration of a weak acid increases, the number of ions increases / decreases /
remains constant.
8.
As
the concentration of a weak acid increases, conductivity increases / decreases /
remains constant.
9.
As
the strength of a weak acid increases, the proportion
of ions to molecules increases / decreases.
10.
As
the strength of a weak acid increases, the conductivity
increases / decreases / remains constant.
11.
What
are the pH values of a weak acid with a concentration of 0.10 and a strong acid with a concentration of 0.01, ten times lower? Weak acid, 0.10 M :__4.0______ Strong Acid, 0.01 M :___2.0____
12.
Explain the significance of the
results of your calculation above. __________________________________
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