Blog Activity 6

1. Complete the teaching idea "Concept questions for chemistry using PheT" posted by Trish Loeblein on the pH scale simulation. 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's an acid, base, or neutral solution. B. False. the color of the solution depends on the pH level.
      2. Which solution is basic? D. more than one. In B and C the pH level is higher than 7. If a pH level is greater than 7 it is known as basic.
      3. Which solution is acidic? C. C has a high level of H3O+
      4. Which solution is basic? B. A is neutral and C is acidic.
      5. Which solution is acidic? D. A and B are more acidic because of the higher levels of Hydronium.
      6. How will adding water effect the pH? A. increase in the pH- by adding more water, the acidity will   decrease .
      7. How will the equal amount of water effect the pH? B. decrease in the pH- more water lessens the basicity, so the pH goes down, but only by .3.
      8. What is the order from most acidic to most basic? A. The higher the pH the more basic it is. The lower the pH the more acidic it is.
      9. What is the order from most acidic to most basic? C. BAC - A is water and water's pH is 7. B has  pH of 13 and C is soda pop having a pH of 2.5.
      10. If a spit has a pH of 7.4, what does that tell you about the water equilibrium? A: something was
added that made the equilibrium shift left. The pH is not 7, meaning something was added. if NaOH was added to the water, OH is in the solution and will react with H3O+ to make the pH go up.

2. Complete the Teaching Idea "intro to Strong and Weak Acids and bases" posted by Chris Bires on the Acid-Base Solutions simulation and post on your blog your data and answers to the questions posed.

Name: Rachael Anderson

Introduction to Strong and Weak Acids and Bases PhET Lab (rvsd 5/2011)

        How does the strength of an acid or base affect conductivity?pH?

Introduction:

When you test your pool’s pH, what are you those little vials or paper strips telling you?  When you hear an acid called “strong” or “weak”, what do those terms refer to?  In aqueous solutions, compounds can exist as molecules (undissociated) or ions (dissociated).  When an acid or a base exists in solution nearly completely as dissociated ions, we refer to that acid or base as strong.  A weak acid or base will donate ions to the solution, but will remain primarily as undissociated molecules.

Notation:

Acids are abbreviated HA, with the H representing the proton (H+) the acid donates to the solution.  The A is referred to as the acidic anion (A-) that is left in solution as the proton is donated.

Strong Bases are abbreviated MOH, with the OH representing the hydroxide ion (OH-) the base donates to the solution.  The M is cation (M+) that is left in solution as the hydroxide is donated..

Autoionization:

Even without any acid or base added a very small number of water molecules will form protons (H+) and hydroxide ions (OH-).  The protons will then form hydronium ions, the acid ion.

Procedure: PhET Simulations à Play With Sims à Chemistryà Acid-Base Solutions à  

The concentration of the acids and bases used in the  at 0.010 (10^-2) Molar.

·         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)	2.00	4.50	12.00	9.50	7.00
pH paper (color)	Red- 2	Orange-5	Blue-12	Green-9	Yellow-7
Conductivity (bright/dim/none)	Bright	Dim	Bright	Dim	none
Exists as Mostly (ions/molecules)	Ions	Molecules	Ions	Molecules	Ions

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	1.00 x10^-2	1.00x10^-2	2.00
	.050 M	Negligible	5.00 x 10^-2	5.00 x 10^-2	1.30
	.100 M	Negligible	1.00 x 10^-1	1.00 x 10^-1	1.00
	1.00 M	Negligible	1.00 x 10^0	1.00 x 10^0	0.00

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	3.87 x 10^-5	3.87 x 10^-5	4.41
	.150 M	1.50 x 10^-1	1.22 x 10^-4	1.22 x 10^-4	3.91
	.015 M	1.93 x 10^-4	1.48 x 10^-2	1.48 x 10^-2	1.83
	.150 M	1.58 x 10^-2	1.34 x 10^-1	1.34 x 10^-1	.87

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	12.00
	.050 M	Negligible	5.00 x 10^-2	5.00 x 10^-2	12.70
	.100 M	Negligible	1.00 x 10^-1	1.00 x 10^-1	13.00
	1.00 M	Negligible	1.00 x 10^0	1.00 x 10^0	14.00

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^-2	3.87 x 10^-5	3.38 x 10^-5	9.58
	.150 M	1.50 x 10^-1	1.22 x 10^-4	1.22 x 10^-4	10.08
	.015 M	1.93 x 10^-4	1.48 x 10^-2	1.48 x 10^-2	12.17
	.150 M	1.58 x 10^-2	1.34 x 10^-1	1.34 x 10^-1	13.13

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 : 5.5          Strong Acid, 0.01 M : 2.00

12.  Explain the significance of the results of your calculation above. There are fewer ions in a weak acid making the pH higher. There are more ions in a strong acid making the pH lower.