1. The Chemistry of Acids and Bases

2. Acids and Bases: Define and Calculate pH/pOH At the conclusion of our time together, you should be able to: 1. Define pH and pOH 2. Explain the pH scale and what it means 3. Change any pH reading to pOH 4. Convert pH to concentration of hydronium ion concentrations, hydronium ion concentrations to pH

3. What is pH??? p = count H = Hydronium ion (H 3 O + ) Measures the concentration of the hydronium ion. Scale ranges from 0-14 < 7 is acidic, more H 3 O + 7 = neutral, H 3 O + = OH- > 7 is basic, OH- > H 3 O +

4. Calculating the pH pH = - log [H+] (Remember that the [ ] mean Molarity) Example: If [H + ] = 1 X 10 -10 pH = - log 1 X 10 -10 pH = 10 Example: If [H + ] = 1.80 X 10 -5 pH = - log 1.80 X 10 -5 pH = 4.7

5. pH Calculations – Solving for H + If the pH of Coke is 3.12, [H + ] = ??? Because pH = - log [H + ] then - pH = log [H + ] Divide both sides by log or Take antilog (10 x ) of both sides and get 10 -pH = [H + ] 10 -3.12 = [H + ] = 7.6 x 10 -4 M *** to find antilog on your calculator, press “Shift” or “2 nd function” and then the log button

6. What is the pOH? A measure or count of the hydroxide ion concentration. It is the opposite of the pH scale. Scale ranges from 0-14 < 7 is basic 7 = neutral > 7 is acidic

7. Calculating the pOH pOH = - log [OH-] (Remember that the [ ] mean Molarity) Example : If [OH - ] = 5.00 x 10 -3 pOH = - log 5.00 x 10 -3 pOH = 2.3

8. pH + pOH = ??? [H+] [OH-] = 1x10 -14 pH + pOH = 14

9. Calculating [H 3 O + ], pH, [OH - ], and pOH Page 13, Row 1. pH = 3.78

10. Calculating [H 3 O + ], pH, [OH - ], and pOH Page 13, Row 2. [H + ] = 3.89x10 -4 M

11. There are Several Ways to Test for pH There are three basic types: Paper pH meter Liquid indicators (Some are natural liquid indicators like red cabbage, radishes)

12. Paper Testing Paper tests like litmus paper and pH paper Put a stirring rod into the solution and stir. Take the stirring rod out, and place a drop of the solution from the end of the stirring rod onto a piece of the paper Read and record the color change. Note what the color indicates. Use a small portion of the paper. You can use one piece of paper for several tests.

13. pH Indicators Indicators are dyes that can be added that will change color in the presence of an acid or base. Some indicators only work in a specific range of pH Once the drops are added, the sample is ruined Some dyes are natural, like radish skin or red cabbage

14. pH Meter Tests the voltage of the electrolyte Converts the voltage to pH Expensive, but very accurate Must be calibrated with a buffer solution

15. The “p” in pH stands for? 1234567891011121314151617181920 21222324252627282930 1. Priority 2. Count 3. Number 4. Molarity 5. Not listed

16. The “H” in pH stands for? 1234567891011121314151617181920 21222324252627282930 1. House 2. Hydrogen ions 3. Acid 4. Concentration 5. Not listed

17. If a solution has a pH of 6.5, what is the pOH of that same solution? 1234567891011121314151617181920 21222324252627282930 1. 4.5 2. 7.5 3. 6.5 4. 0.0 5. 12.5 6. Not listed

18. If a solution has a pH of 6.2, what is the [H + ] of that solution? 1234567891011121314151617181920 21222324252627282930 1. 6.2 2. 6.3 x 10 -7 3. 1.0 x 10 6.2 4. 1.0 x 10 7.8 5. 7.8 6. Not listed

19. If a solution has a pOH of 9.44, what is the [OH - ] of that same solution? 1234567891011121314151617181920 21222324252627282930 1. 0.98 2. 1.00 x 10 9.44 3. 3.63 x 10 -10 4. 4.56 5. 9.44 6. Not listed

20. Red litmus paper will turn what color in an acid? 1234567891011121314151617181920 21222324252627282930 1. Blue 2. White 3. Red 4. Clear 5. Not listed

21. Which of the following would be the most accurate way to test for pH? 1234567891011121314151617181920 21222324252627282930 1. pH meter 2. Litmus paper 3. Phenylthalein 4. Cabbage juice 5. Universal indicator 6. Not listed

22. Several liquids are tested for pH. Which of these liquids would be the weakest acid? 1234567891011121314151617181920 21222324252627282930 1. Liquid a, pH = 1.0 2. Liquid b, pH = 4.5 3. Liquid c, pH = 6.5 4. Liquid d, pH = 8.5 5. Liquid e, pH = 10.5 6. Liquid f, pH = 13.0

23. If a solution has a [H 3 O + ] of 6.20 x 10 -8, what is the pH of that solution? 1234567891011121314151617181920 21222324252627282930 1. 6.79 2. 8.79 3. 5.21 4. 4.56 5. 7.21 6. Not listed

24. If a solution has a [OH - ] of 1.05 x 10 -3, what is the pH of that solution? 1234567891011121314151617181920 21222324252627282930 1. 11.02 2. 2.98 3. 1.00 4. 3.02 5. 10.98 6. Not listed

25. Extra Quiz Questions Name these: HBr HNO 4 H 2 CO Fe(OH) 2 H 2 SO 4 Write the formula: Hydroselenic acid Phosphoric acid magnesium hydroxide Sulfurous acid Perbromic acid