1. REMINDER: NO LAB THIS WEEK EXAM CLARIFICATION/FRIDAY DEADLINE SET CLICKER TO CHANNEL 41 Announcements

2. Bases Strong bases are hydroxide salts For now, only important weak base is NH 3  Ionization of weak acid produces a weak base

3. If the oxalate anion (C 2 O 4 - ) reacts in an acid-base reaction, which of the following can’t it make? 1. H 2 C 2 O 4 2. HC 2 O 4 - 3. 2CO 2

4. Acid Base Reactions

5. Strong Acid + Strong Base HCl(aq) + NaOH(aq)  NaCl(aq) + H 2 O(l) acid base “salt” water What do we get if we mix: HBr (aq) + LiOH (aq) 

6. Acid Base Reactions Diprotic acids or bases H 2 SO 4 (aq) + NaOH(aq)  H 2 SO 4 (aq) + Ba(OH) 2 (aq)  HCl(aq) + Ba(OH) 2 (aq) 

7. Acid Base Reactions Strong Acid + Weak Base HCl(aq) + NH 3 (aq)  What do we get if we mix: HNO 3 (aq) + NH 3 (aq) 

8. Acid Base Reactions Weak Acid + Strong Base (like strong acid+strong base) HCN(aq) + NaOH(aq)  NaCN(aq) + H 2 O(l) acid base “salt” water What do we get if we mix: HCOOH (aq) + KOH (aq)  formic acid

9. Net Ionic Equations 1. Write a balanced chemical equation  Molecular equation 1. Write out all the ions  Total ionic equation 2. Cancel out anything that appears on both sides  Net ionic equation

10. Net Ionic Equations HCl(aq) + NaOH(aq)  NaCl(aq) + H 2 O(l) What really happens: H + (aq) + OH - (aq)  H 2 O(l) Sodium ion and chloride ion are “spectator ions”

11. Reactions Involving a Weak Base Molecular equation: HCl(aq) + NH 3 (aq)  NH 4 Cl(aq) Total ionic equation: H + (aq) + Cl - (aq) + NH 3 (aq)  NH 4 + + Cl - (aq) Net ionic equation: H + (aq) + NH 3 (aq)  NH 4 + (aq) What is the net ionic equation for: HNO 3 (aq) + NH 3 (aq)  NH 4 NO 3 (aq)

12. CH 3 CO 2 H(aq) + NaOH(aq)  1. CH 3 CO 2 H 2 + (aq) + NaO(aq) 2. CH 3 CO 2 - (aq) + H 2 O(l) + Na + (aq) 3. CH 4 (g) + CO 2 (g) + H 2 O(l) 20

13. HCN(aq) + NH 3 (aq)  20 1. NH 4 + (aq) + CN - (aq) 2. H 2 CN + (aq) + NH 2 - (aq) 3. C 2 N 2 (s) + 3 H 2 (g)

14. The pH Scale Quantitative measure of solution acidity Remember solution concentration:   [NaCl]=0.25M means 0.25 moles of NaCl are in 1L of solution

15. The pH Scale In pure water, some molecules ionize to form H 3 O + and OH - H 2 O + H 2 O  OH – + H 3 O + In acidic and basic solutions, these concentrations are not equal acidic: [H 3 O + ] > [OH – ] basic: [OH – ] > [H 3 O + ] neutral: [H 3 O + ] = [OH – ]

16. The pH Scale pH scale= measure of [H 3 O + ] pH < 7.0 = acidic pH > 7.0 = basic pH = 7.0 = neutral Measure of H 3 O + concentration (moles per liter) in a solution As acidity increases, pH decreases

17. The pH Scale The pH scale is logarithmic 10010 2 log(10 2 ) = 2 1010 1 log(10 1 ) = 1 110 0 log(10 0 ) = 0 0.110 –1 log(10 –1 ) = –1 0.0110 –2 log(10 –2 ) = –2 pH = –log [H 3 O + ] pH = –log [H 3 O + ] pH if [H 3 O + ] = 10 –5 ? 10 –9 ? pH if [H 3 O + ] = 10 –5 ? 10 –9 ? Acidic or basic? pH if [H 3 O + ] = 0.000057 M? pH if [H 3 O + ] = 0.000057 M?

18. Finding [H 3 O + ] from pH [H 3 O + ] = 10 -pH or [H 3 O + ] = log -1 (-pH) [H 3 O + ] = 10 -pH or [H 3 O + ] = log -1 (-pH) Finding the inverse log (or log -1 )of a number on your calculator: Finding the inverse log (or log -1 )of a number on your calculator: Enter the number, press the inverse (inv) or shift button, the press the log button (it might be labeled 10 x ) What is [H 3 O + ] if pH = 8.6? What is [H 3 O + ] if pH = 8.6?

19. pH: Quantitative Measure of Acidity Acidity is related to concentration of H + (or H 3 O + ) pH = -log[H 3 O + ] [H 3 O + ]=10 -pH =log -1 (-pH)