1. Chapter 10 Acids and Bases (10.1) Acid-Base Strength

2. Strong Acid (SA) an acid that dissociates completely into ions in water Ex.)all molecules of HCl (aq) dissociate into H + and Cl - ions the H + ions that are formed bond with H 2 O to form H 3 O + HCl (aq) + H 2 O (l)  H 3 O + (aq) + Cl - (aq)

3. Strong Acid (SA) other SA’s are….. HBr HI HNO 3 H 2 SO 4 HClO 4

4. Concentration the conc. of H 3 O + (aq) ions, [H 3 O + ], in a dilute solution of a SA is equal to the conc. of the acid, [acid] [H 3 O + ] = [strong acid] Ex.) In a sample of 1.0 mol/L HCl (aq) [H 3 O + ] = 1.0 mol/L square bracket Molar Concentration Recall: C = n V

5. Dissociation (Strong Acid) Text p 381 Figure 10.6 100% of hydrogen chloride molecules dissociate

6. Dissociation (Weak Acid) Text p 382 Figure 10.7 1% of acetic acid molecules dissociate. In solution there are mostly acetic acid molecules and only some ions.

7. Weak Acid (WA) an acid that dissociates very slightly into ions in water Ex.) not all molecules of CH 3 COOH (aq) break apart, some remain intact only about 1% of acetic acid molecules dissociate In a sample of 1.0 mol/L CH 3 COOH (aq), [H 3 O + ] <<< 1.0 mol/L That is, [H 3 O + ] < [weak acid]

8. Strong Base (SB) a base that dissociates completely into ions in water Ex.) all molecules of NaOH (aq) dissociate into Na + and OH - ions other SB’s are… KOH Ca(OH) 2 Ba(OH) 2

9. Concentration the conc. of OH 1- (aq) ions, [OH 1- ], in a dilute solution of a SB is equal to the conc. of the base, [base] [OH 1- ] = [strong base] Ex.) In a sample of 1.0 mol/L NaOH (aq) [OH 1- ] = 1.0 mol/L

10. Weak Base (WB) most bases are weak WB dissociates very slightly into ions in water Ex.) ammonia [OH 1- ] < [weak base]

11. Acid Dissociation few acids contain only a single H + ion monoprotic acid: produces one H + ion Ex.) HF (aq) + H 2 O (l)  H 3 O + (aq) + F - (aq) (simplified) HF (aq)  H + (aq) + F - (aq)

12. Acid Dissociation many acids contain 2 or more H + ions diprotic acid: produces two H + ions Ex.) H 2 SO 4 (aq)  H + (aq) + HSO 4 - (aq) HSO 4 - (aq)  H + (aq) + SO 4 2- (aq) H 2 SO 4(aq)  2H + (aq) + SO 4 2- (aq)

13. Acid Dissociation triprotic acid: produces three H + ions Ex.) H 3 PO 4 (aq)  H + (aq) + H 2 PO 4 - (aq) H 2 PO 4 - (aq)  H + (aq) + HPO 4 2- (aq) HPO 4 2- (aq)  H + (aq) + PO 4 3- (aq) H 3 PO 4(aq)  3 H + (aq) + PO 4 3- (aq)

14. Measuring Strength – pH Scale In pure water, [H 3 O + ] = [OH - ] = 1.0 x 10 -7 mol/L In acidic sol’n, [H 3 O + ] > [OH - ] In basic sol’n, [H 3 O + ] < [OH - ]

15. Measuring Strength – pH Scale In any aqueous sol’n the product can be calculated, [H 3 O + ] x [OH - ] = 1.0 x 10 -14 The values of [H 3 O + ] range from 10 mol/L to 10 -15 mol/L

16. pH Scale We use system of logarithms to handle the range of exponents for [H 3 O + ] Ex.) log (1x10 2 ) = 2 log (1x10 -6 )= - 6 simply, use the exponent when the value is written as 1 x base 10 or use your calculator

17. pH Scale Ex.) [H 3 O + (aq) ] = 1.0 x10 -4 pH= -log[1.0 x10 -4 ] = +4 pH = -log[H 3 O + (aq) ]

18. pH Scale Calculate, 1)pH if [H 3 O + (aq) ] = 3.8 x10 -3 mol/L (ans: 2.42) 2) [H 3 O + (aq) ] if pH = 3.85 (ans: 1.4 x 10 -4 mol/L) 3) pH of 0.082 mol/L HCl (aq) (ans: 1.09) [H 3 O + (aq) ] = 10 -pH

19. pOH Scale Ex.) [OH - (aq) ] = 1.0 x10 -6 pH= -log[1.0 x10 -6 ] = +6 pOH = -log[OH - (aq) ] pOH + pH = 14

20. Homework