Friday, January 18, 2013

Activity #8 (Half)


Activity 8: Exploration of Chemistry
For activity 8, students have a choice to explore other topics of chemistry presented in the PhET simulations. 

Tasks to be completed:

1. Choose any Teaching Idea from any of the Chemistry Simulations (http://phet.colorado.edu/en/simulations/category/chemistry ) and post your results/data and/or answers on your blog.

1. Which picture best displays atoms?
D.

2. Which picture displays 2NH3?
D. Two are correct

3. Which could be hydrochloric acid?
A.

4. Which could be CO2?
B.

5. What is the name of this molecule?
Methane

6. What is the name of this molecule?
D. Water

7. What is the name of this molecule?
C. Chlorine 

Activity #7

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. __________________________________