pH Scale Questions:
1. The color of a solution identifies if it is an acid, base, or neutral solution.
True- Acids will turn litmus red. Bases will turn litmus blue. Neutral solutions will stay the same as they have equal amounts of acids and bases.
2. Which solution is basic?
The higher the pH level in a solution the more basic it is therefore the answer is C (pH 12.06)
3. Which solution is acidic?
The lower the pH level the more acidic a solution is therefore the answer is C. You can see from the pictures that it contains H3O ions which are positive creating an acidic solution.
See picture at this web address under pH Scale- Pg 24 http://phet.colorado.edu/en/contributions/view/3214
See picture at this web address under pH Scale- Pg 24 http://phet.colorado.edu/en/contributions/view/3214
4. Which solution is basic?
The solution that is basic is answer B. As you can see from the picture that there are the most blue (basic) ions in this column creating a basic solution.
See picture at this web address under pH Scale- Pg 24 http://phet.colorado.edu/en/contributions/view/3214
See picture at this web address under pH Scale- Pg 24 http://phet.colorado.edu/en/contributions/view/3214
5. Which solution is acidic?
The solution that is acid is answer A. As you can see in the picture there are the most red (acidic) ions in this column therefore creating the most acidic solution.
See picture at this web address under pH Scale- Pg 24 http://phet.colorado.edu/en/contributions/view/3214
6. How will adding water effect the pH lever?
When water is added to the solution it will decrease the acidity. Because the acidity goes down the pH goes up. (Answer A)
7. How will equal amount of water effect the pH?
Having equal amounts of water as shown in the picture will decrease the pH because it will lessen the basicity. (Answer B)
8. What is the order from most acidic to most basic?
The order from most acidic to most basic is: pH 6.50, pH 7.40, pH 12.06. The higher the pH level the more basic the solution is. (Answer A)
9. What is the order from most acidic to most basic?
The order from most acidic to most basic is Answer E (CAB) . As you can see when they are all lined up in the CAB order that the red lines (Acidic) go high to low as the blue lines (Basic) go from low to high.
See picture at this web address under pH Scale- Pg 24 http://phet.colorado.edu/en/contributions/view/3214
10. If spit has a pH=7.4, what does that tell you about the water equilibrium?
If water is 7 and spit is 7.4 then something was added to the solution to make the equilibrium shift to the left. (Answer A)
Introduction to Strong and Weak Acids and Bases PhET Lab (rvsd 5/2011)
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.
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. .
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
· 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 | 4.50 | 12.00 | 9.50 | 7.00 |
pH paper (color) | Red | Orange | Blue | Green (9) | Yellowish/Orange (7) |
Conductivity (bright/dim/none) | Bright | Weak | Bright | Weak | Little to None |
Exists as Mostly (ions/molecules) | Ion | Molecules | Ions | Molecules | Molecules/ Ions |
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 x 10-2 | 1.00x10 -2 | 2.00 | |
.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 | 1.00 | |
1.00 M | Negligible | 1.00 x 10 0 | 1.00 x 10 0 | 0 |
Weak Acids
Strength (approximately) | Initial Acid Concentration (mol/L) | [HA] (mol/L) | [A-] (mol/L) | [H+] (mol/L) | pH |
.015 M | 1.51 x 10 -2 | 3.88 x 10 -5 | 3.88 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 | 6.62 x 10 -4 | 1.43 x 10 -2 | 1.43 x 10-2 | 1.84 | |
.150 M | 3.94 x 10 -2 | 1.11 x 10 -1 | 1.11 x 10 -1 | .96 |
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 | 12.70 | |
.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 |
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 | 2.94 x 10 -5 | 2.94 x 10-5 | 9.47 | |
.150 M | 1.50 x 10 -1 | 9.29 x 10 -5 | 9.29 x 10 -5 | 9.97 | |
.015 M | 3.95 x 10 -4 | 1.46 x 10-2 | 1.46 x 10 -2 | 12.16 | |
.150 M | 2.77x 10 -2 | 1.22 x 10 -1 | 1.22 x 10 -1 | 13.09 |
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. Less molecules in strong acid because of it's concentration.
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