1. Tuesday, May 20th (P1/2) PDN: Name H(NO3) and HI Write the formula for zinc (II) hydroxide and phosphoric acid Daily Log: Review Naming Acids and Bases Take Home due tomorrow Quiz on Thursday!

2. Tuesday, May 20 th (P 6/7) PDN: Name Co(OH) 3 Write the formula for nitrous acid Daily Log: Review Naming Quiz Tomorrow pH notes

3. Section 20.2 Hydrogen Ions and Acidity OBJECTIVES: Given the hydrogen-ion or hydroxide-ion concentration, classify a solution as neutral, acidic, or basic.

4. Section 20.2 Hydrogen Ions and Acidity OBJECTIVES: Convert hydrogen-ion concentrations into values of pH, and hydroxide-ion concentrations into values of pOH.

6. pH pH is a measure of the acidity or basicity of an aqueous solution.

7. Logarithms and the pH concept definition: pH = -log[H + ] (Logarithms are powers of ten.) Neutral solution: pH = 7 Acidic solution: pH = less than 7 Basic solution: pH= greater than 7

8. pH and pOH pOH = -log [OH - ] pH + pOH = 14 Basic Solution: pOH = less than 7 Acidic Solution: pOH = greater than 7

9. Calculation Practice What is the pH and pOH of a 1.2 x 10 -3 M HBr solution? FIRST ASK YOURSELF: IS HBr AN ACID OR A BASE?

10. Calculation Practice: What is the pH and pOH of a 2.34 x 10 -5 M NaOH solution? FIRST ASK YOURSELF: IS NaoH AN ACID OR A BASE?

11. Calculation Practice: Determine the [H 3 O + ] of a solution with a pH of 2.81 Determine the [OH-] of a solution with a pH of 11.21

12. Calculation Practice Determine the pH of a magnesium hydroxide solution in which 17.1 grams are dissolved in 1L.

13. Measuring pH Why measure pH? Everything from swimming pools, soil conditions for plants, medical diagnosis, soaps and shampoos, etc. Sometimes we can use indicators, other times we might need a pH meter

14. Acid-Base Indicators An indicator is an acid or base that undergoes dissociation in a known pH range, and has different colors in solution (more later in chapter) Examples: litmus, phenolphthalein, bromthymol blue:

15. Acid-Base Indicators Although useful, there are limitations to indicators: usually given for a certain temperature (25 o C), thus may change at different temperatures what if the solution already has color? Ability of human eye to distinguish colors

16. Acid-Base Indicators A pH meter may give more definitive results Gives numerical pH values some are large, others portable works by measuring the voltage between two electrodes needs to be calibrated