2. Acids and Bases Chapters 15

3. I. Introduction A. Characteristics of acids 1) formulas BEGIN with Hydrogen 2) taste sour 3) turn blue litmus paper to RED 4) react with and neutralize bases B. Characteristics of Bases 1) formulas typically END with OH 2) taste bitter 3) feel slippery 4) turn red litmus paper BLUE 5) react with and neutralize acids

4. I. Review of Acid Nomenclature A. Binary acids hydro + (root) +ic acid ex: HCl - hydrochloric acid HI - hydroiodic acid B. Polyatomic acids (a.k.a oxyacids) 1) polyatomic ions ending with -ATE (root) + ic acid ex: H 2 SO 4 - sulfuric acid HClO 3 - chloric acid 2) polyatomic ions ending with -ITE (root) + ous acid ex:HNO 2 - nitrous acid

5. Practice Nomenclature a) HClO 2 b) H 2 S c) HIO 4 d) HBrO e) HMnO 4 f) H 2 CrO 4 g) HOH

6. II. Conjugate Acid and Base Theory A. Behaving like an Acid means to GIVE AWAY a H-atom B. Behaving like a Base means to ACCEPT an H-atom C. Ionization reactions always involve acid/base pairs: ex: HCN + H 2 O CN - + H 3 O + acid conj. acid base conj. base ex: NH 3 + H 2 O NH 4 + + OH - base conj. acid acid conj. base amphoteric - able to act as either acid or base

7. Do Now 1) Indicate the conjugate base of H 2 S 2) Indicate the conjugate acid of HSO 4 - 3) Indicate the conjugate base of HPO 4 -2 4) Indicate the conjugate acid of HCO 3 -

8. notes: 1) acids lose H to become a conjugate base 2) bases accept H to become a conjugate acid 3) WEAK “originals” make STRONG conjugates 4) STRONG “originals” make WEAK conjugates ex: HCN + H 2 O CN - + H 3 O + weakstrongweakstrong ex: NH 3 + H 2 O NH 4 + + OH - weak strong notes: 1) H 3 O + is always a STRONG ACID 2) OH - is always a STRONG BASE

9. Strengths of Acids I.Binary acids A. Within a group … 1) the weaker the bond the stronger the acid 2) weaker bonds occur with larger anions B. Within a period 1) the more electronegative anion the stronger the acid ex: Arrange this from weaker (1) to stronger HIHFHClHBr

10. Strengths of Acids II. Oxyacids A. With the same # of oxygens… - more electronegative center = stronger B. Same atoms, more oxygens - the more oxygen there are = stronger the acid HClO HClO 2 HClO 3 HClO 4 HClO HBrO HIO

11. III. Strengths of Acids and Bases A. Strong acids HCl HBr HI HNO 3 HClO 3 HClO 4 H 2 SO 4 B. Strong bases (Group IA) - OH (Group IIA) - OH Weak acids all the others Weak bases NH3 covalent compounds with C, H, N in the formulas ex: HF CH 3 NH 2 Ca(OH) 2 HNO 2 Na 2 CO 3

12. IV. Acid - Base Theories A. Three prevailing theories exist to define acids/bases 1) Arrhenius - acids = H in formula - bases = OH in formula ex: HCl LiOH 2) Bronsted - Lowry - acids = proton donor - bases = proton acceptor ex: HCl NH 3 3) Lewis - acids = electron pair acceptor - bases = electron pair donor ex: BF 3 NH 3

13. DO NOW H 2 O + HC 2 H 3 O 2 => H 3 O + + C 2 H 3 O 2 - Identify the acid/bases and conjugate acid bases and then identify as weak or strong.

14. ex: HCN + H 2 O CN - + H 3 O + ex: NH 3 + H 2 O NH 4 + + OH - Bronsted acids:Bronsted bases

15. V. The pH Scale A. Concentrations of H + and OH - are often converted to a more convenient mathematical form: 1) pH = - log [H + ] ex: instead of [H + ] = 1.00 x10 -6 M........ pH = 6.000 How? pH = - log (1.0 x 10 -6 ) = 6.00 2) pOH = - log [OH - ] ex: instead of [OH - ] = 2.0 x10 -3 M........ pOH = 2.70 How? pOH = -log (2.0 x10 -3 ) = 2.70

16. B. The ionization of water causes the product of [H + ] and [OH - ] to always equal a constant: 1) [H + ] [OH - ] = 1.0 x 10 -14 (known as K w ) 2) If the concentration of one is known, the other can be calculated Ex: [H + ] = 1.00 x 10 -4 M...... [OH -1 ] = 1.00 x 10 -10 M OR...... If pH = 4, then pOH = ????? pOH = 10

17. Practice: 1)What is the pH of 2.50 x 10 -3 M HCl? 2) What is the pOH of 3.5 x 10 -8 M HNO 3 ? 3) What is the [H + ] of a solution with pH = 9.20? 4) What is the [OH - ] of a solution with pH = 6.85?

18. C. Acidic/Basic solutions are determined by their pH values: 1) pH < 7....... acidic 2) pH > 7....... basic 3) pH = 7....... neutral

19. pH Chart Showing Common Substances

20. Try It Now Write the reaction that occurs when NaOH is added to HCl.

21. VI. Acid-Base Titrations A.An acid and a base react to form: NaOH + HCl  NaCl + H 2 O base + acid  salt + water B. Neutralization 1) occurs when an acid and a base react 2) same as double replacement reaction

22. C. A solution is neutral when moles acid = moles base Ex: Suppose 42.00 mL of a 0.150 M NaOH solution is required to neutralize 50.00 mL of an unknown HCl solution. What is the molarity of the HCl solution? Answer: 0.126 M HCl

23. Ex: Suppose 42.00 mL of a 0.150 M NaOH solution is required to neutralize 50.00 mL of an unknown H 2 SO 4 solution. What is the molarity of the H 2 SO 4 solution? Answer: 0.0630 M H 2 SO 4

24. Ex: If 50.00 mL of a 0.2000 M HCl solution is titrated with 0.1500 M NaOH…. a)What is the pH before any NaOH has been added? b)What is the pH after 10.00 mL of base has been added? a)What is the pH after 70.00 mL of base have been added?

25. Review 1)List 3 characteristics of acids and bases 2) What is the conjugate base of OH - ? 3)What is the [OH - ] of 2.5 x 10 -8 M HCl? 4)Write the formula for hydroiodic acid. 5)Identify NH 3 as Arrhenius acid/base, Bronsted acid/base, or Lewis acid/base

26. Review 6) What is the pH of 3.0 x 10 -4 M NaOH? 7) What is the pH after 5.0 mL of 0.20 M HCl is titrated with 8.0 mL of 0.10M NaOH? 8) How many mL’s of 0.250 M NaOH are required to neutralize 30 mL of 0.15M HCl? 9) Which acid is strongest … HIO or HIO 3 10) Which base is strongest … Cl - or F - ?