Sunday, July 10, 2011

Activity 7

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. There are 2 balloons in a room. They are identical in size and material. One balloon is filled with air and the other balloon is filled with Helium. How does the pressure of the air balloon compare to the pressure of the Helium balloon. The pressure in the air balloon is

Less
2. How does the pressure in the Helium balloon compare to the pressure of the air in the room? The pressure in the Helium balloon is 
Greater
3.  How do the number of air molecules in the air balloon  compare to the number of He atoms in Helium balloon? The number of air molecules is 
Less
4. How does the average speed of the Helium molecules compare to that of the air molecules?
The average speed of the He molecules is
Greater

5. What will happen to the pressure if temp is held constant and the volume is decreased?
Pressure goes up
 6. You are flying from Denver to Boston, and you bring along a ½ full bottle of shampoo that was well sealed before you left Denver. You land in Boston and proceed to your hotel. The number of air molecules within the shampoo bottle: 

Has increased


7.  If the walls of the shampoo bottle are strong and rigid so that the bottle has the same shape as before you left, how does the pressure of the air inside the bottle compare to the pressure of the air in Denver?

Greater than  

 

8.  How does the pressure inside the bottle compare to the pressure of the air in Boston?

Equal to


9. If you had a water bottle with very soft sides. When you open your suitcase in Boston, the bottle would look
Puffed Out


 
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.




Strong Acid
Weak Acid
Strong Base
Weak Base
Water
pH meter read
(value)
2.00
4.50
12.00
9.50
7.00
pH paper
(color)
red
orange
navy
green
Light orange
Conductivity
(bright/dim/none)
Very bright
average
Very bright
bright
dim

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
Neg
1.00x10-2
1.00x10-2
2
.050 M
Neg
5.00x10-2
5.00x10-2
1.3
.100 M
Neg
1.00x10-1
1.00x10-1
1
1.00 M
Neg
1.00x10 0
1.00x10 0
0

Weak Acids

Strength (approximately)
Initial Acid Concentration (mol/L)
[HA] (mol/L)
[A-] (mol/L)
[H+] (mol/L)
pH
.015 M
1.49x10-2
7.29x10-5
7.29x10-5
4.14
.150 M
1.50x10-1
2.31x10-4
2.31x10-4
3.64
.150 M
1.85x10-2
1.32x10-1
1.32x10-1
.88
.015 M
2.33x10-4
1.48x10-2
1.48x10-2
1.83

Strong Bases

Strength
Initial Acid Concentration (mol/L)
[MOH] (mol/L)
[M+] (mol/L)
[OH-] (mol/L)
pH
.010 M
Neg
1.00x10-2
1.00x10-2
12
.050 M
Neg
5.00x10-2
5.00x10-2
12.7
.100 M
Neg
1.00x10-1
1.00x10-1
13
1.00 M
Neg
1.00x10 0
1.00x10 0
14

Weak Bases

Strength (approximately)
Initial Acid Concentration (mol/L)
[B] (mol/L)
[BH+] (mol/L)
[OH-] (mol/L)
pH
.015 M
1.50x10-2
4.20x10-5
4.20x10-5
9.62
.150 M
1.50x10-1
1.33x10-4
1.33x10-4
10.12
.015 M
1.64x10-4
1.48x10-2
1.48x10-2
12.17
.150 M
1.38x10-2
1.36x10-1
1.36x10-1
13.13

Conclusion Questions:
1.      A strong acid is very concentrated.
2.      A weak base is a weak electrolyte.
3.      A strong base is a strong electrolyte.
4.      At the same concentration (Molarity) a strong acid will have a lower.
5.      As concentration of a weak acid increases, the pH decreases.
6.      As concentration of a weak base increases, the pH increases.
7.      As the concentration of a weak acid increases, the number of ions increases.
8.      As the concentration of a weak acid increases, conductivity increases.
9.      As the strength of a weak acid increases, the proportion of ions to molecules 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 Strong Acid, 0.01 M : 2


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