Acids, Bases and pH Chapter 19

Compounds That Become Acids When Dissolved in Water General Formula: HX H + X - monatomic or polyatomic anion

Naming Acids (p. 250) Binary acids Hydro_______ic Acid HCl: Hydrochloric acid HBr: Hydrobromic acid HS: Hydrosulfuric acid Oxyacids ite becomes ous Acid from chlorite: HClO 2 = chlorous acid Acid from phosphite: H 3 PO 3 = phosphorous acid ate becomes ic Acid from sulfate: H 2 SO 4 = sulfuric acid

Compounds That Become Acids When Dissolved in Water Your turn: HBr HNO 2 HNO 3

Compounds That Become Acids When Dissolved in Water Your turn: HBr hydrobromic acid HNO 2 nitrous acid HNO 3 nitric acid

Practice Name or write formulas for the following acids: 1. Phosphoric Acid5. HClO 4 2. Hydrochloric Acid6. HI 3. Chlorous Acid7. H 2 S 4. Sulfurous Acid8. HC 2 H 3 O 2 9. Write the balanced formula, total ionic and net ionic equations for the acid base neutralization reaction that occurs when aqueous sulfuric acid is mixed with aqueous potassium hydroxide

Practice Name or write formulas for the following acids: 1. phosphoric acid H 3 PO 4 2. hydrochloric acid HCl 3. chlorous AcidHClO 2 4. sulfurous Acid H 2 SO 3 5. HClO 4 perchloric acid 6. HI hydroiodic acid 7. H 2 S hydrosulfuric acid 8. HC 2 H 3 O 2 acetic acid

Practice 9. Write the balanced formula, total ionic and net ionic equations for the acid base neutralization reaction that occurs when aqueous sulfuric acid is mixed with aqueous potassium hydroxide (put answer on front whiteboard)

Properties of Acids and Bases AcidsBases Taste sourTaste bitter Feel wetFeel slippery Turn litmus REDTurn litmus BLUE Conduct electricity React with most metalsDo NOT react with most metals Contain more H + than OH - Contain more OH - than H + pH between 0 and 7pH between 7 and 14 strong acid + strong base  salt + H 2 O

Arrhenius acids and bases Acid: compound containing H that ionizes to yield H + in solution HCl (g) H + (aq) + Cl - (aq) HCl (g) + H 2 O (l) H 3 O + (aq) + Cl - (aq) Base: compound containing OH that ionizes to yield OH - in solution NaOH (s) Na + (aq) + OH - (aq) *Note: Every Arrhenius acid/base is also a Brønsted-Lowry acid/base.

Autoionization of Water In pure water : [H 3 O + ] = 1.0 x M AND [OH - ] = 1.0 x M If we add acid [H 3 O + ] increases and [OH - ] decreases. [H 3 O + ] = 1.0 x M [OH - ] = 1.0 x M If we add base, the reverse is true: [H 3 O + ] = 1.0 x M [OH - ] = 1.0 x M What is the product of [H 3 O + ] x [OH - ] in each case?

The pH Scale pOH = - log [OH - ] = - log (1.0 x ) = -(-7) = 7 pH = - log [H + ] = - log (1.0 x ) = -(-7) = 7 Pure Water basis of neutral pH 7:[H + ] = [OH - ]

Concentration, pH and pOH (for strong acids and bases) Concentration is given in terms of molarity (M) Concentration of H + = [H + ] = = M In scientific notation: [H + ] = 1.00 x M Find pH: pH = -log[1.00 x M] pH = 2 Find pOH: pH + pOH = 14 pOH = 12 Find [OH-]: [OH-] = 10 -pOH = [OH - ] = 1.00 x M

Converting between Concentration and pH pHpHpOH [H+][H+][OH - ] pHpHpOH[H+][H+][OH - ] 1.00 x M x M 1.00 x M x M

Practice pH + pOH = 14; pH = -log[H + ]; pOH = -log[OH - ] When pH = 2 [H + ] = _____________M pOH = ____________ [OH - ] = ____________M When pOH = 8 [OH - ] = ___________ M pH = _____________ [H + ] = ____________ M [H + ] = 1.0 x MWhat is the [OH - ]?

More Practice (HW) 1. What is the pH of a solution with a [H + ] of M? 2. What is the pOH of a solution with a [OH - ] of M? 3. What is the pH of a solution with a [OH - ] of M? 4. What is the pOH of a solution with a [H + ] = M? 5. Which is more acidic, a solution with a pH of 6 or one with a pH of 9? 6.Which is more basic, a solution with a pOH of 7 or one with a pOH of 12? 7.Which is more acidic, a solution with a pH of 5 or one with a pOH of 10? 8.Which is more basic, a solution with a pH of 8 or one with a pOH of 12?

More Practice 1. What is the pH of a solution with a [H + ] of M? 8 2. What is the pOH of a solution with a [OH - ] of M? What is the pH of a solution with a [OH - ] of M? What is the pOH of a solution with a [H + ] = M? 9 5.Which is more acidic, a solution with a pH of 6 or one with a pH of 9? pH of 6 6.Which is more basic, a solution with a pOH of 7 or one with a pOH of 12? pOH of 7 7.Which is more acidic, a solution with a pH of 5 or one with a pOH of 10? pOH of 10 8.Which is more basic, a solution with a pH of 8 or one with a pOH of 12? pH of 8

More Practice 9.Stomach contents can have a pH of 3. Are stomach contents acidic, basic or neutral? 10. Pure water has a pOH of 7. Is pure water acidic, basic or neutral? 11.Normal rain has a pH of approximately 6. Is normal rain strongly acidic, slightly acidic, neutral, slightly basic, or strongly basic? 12.Acid precipitation is often a problem in industrialized areas. What might you expect the pH of acid rain to be?

More Practice 9. Stomach contents can have a pH of 3. Are stomach contents acidic, basic or neutral? acidic 10. Pure water has a pOH of 7. Is pure water acidic, basic or neutral? neutral 11.Normal rain has a pH of approximately 6. Is normal rain strongly acidic, slightly acidic, neutral, slightly basic, or strongly basic? slightly acidic 12. Acid precipitation is often a problem in industrialized areas. What might you expect the pH of acid rain to be? < 6

Strong acid or base – ionizes/dissociates completely in water [H + ] or [OH - ] = conc. of acid or base. e.g. HCl, NaOH. 5 units of acid – 5 out of 5 dissociated H + Cl - H + Cl - H + Cl - H + Cl - H + Cl - Weak acid or base – ionizes/dissociates only partially in water [H + ] or [OH - ] < conc. of acid or base. e.g. HC 2 H 3 O 2, NH 3 5 units – only 1 out of 5 dissociated HC 2 H 3 O 2 HC 2 H 3 O 2 HC 2 H 3 O 2 HC 2 H 3 O 2 H + C 2 H 3 O 2 - Strength of Acids and Bases

Strengths of Acids and Bases Strong  concentrated Weak  dilute A concentrated weak acid (or base) may have the same pH as a dilute strong acid (or base).

Strong vs. Weak Demo Strong acid: HCl + H 2 O  Cl - + H 3 O x M ? M pH = ? Weak acid: HC 2 H 3 O 2 + H 2 O ↔ C 2 H 3 O H 3 O x M ? M pH = ? Strong base: NaOH + H 2 O  Na + + OH x M ? M pH = ? Weak base: NH 3 + H 2 O ↔ NH OH x M ? M pH = ?

Strong and Dilute vs. Weak and Concentrated Acids: Strong HClWeak HC 2 H 3 O 2 Weak HC 2 H 3 O 2 Dilute Dilute Conc 100 x 0.01 M0.01 M 1M pH = pH = pH = Bases: Strong NaOH Weak NH 3 Weak NH 3 DiluteDilute Conc 100 x 0.01M0.10 M 1M pH = pH = pH =

What do you think? Table salt Vinegar Rubbing alcohol Window Cleaner Distilled water Lemon juice Soap Drain cleaner Applesauce Blood Are the following acidic, basic or neutral? What is the difference between a strong acid and a concentrated acid? A weak acid and a dilute acid?

Warm up 1.Write formulas for the following acids: a) hydroiodic acid b) chlorous acid c) chloric acid d) perchloric acid (Honors) e) hypochlorous acid (Honors) f) phosphoric acid g) phosphorous acid

Warm up 1.Write formulas for the following acids: a) hydroiodic acidHI b) chlorous acidHClO 2 c) chloric acidHClO 3 d) perchloric acid HClO 4 (Honors) e) hypochlorous acid HClO (Honors) f) phosphoric acidH 3 PO 4 g) phosphorous acidH 3 PO 3 (Honors)

Brønsted-Lowry Acids and Bases (1923) Acid: H + (proton) donor Base: H + (proton) acceptor HCl + H 2 O  H 3 O + + Cl - acid base conjugate conjugate acid base

Brønsted-Lowry Acids and Bases (1923) NH 3 + H 2 O D NH OH - ammonia water ammonium ionhydroxide ion (B-L base) (B-L acid) (B-L acid) (B-L base) base acid conjugate acid conjugate base

Conjugate Acid-Base Pairs Conjugate acid = species produced when a base accepts a hydrogen ion from an acid Conjugate base = species that results when an acid donates a hydrogen ion to a base

Identify the conjugate acid-base pairs: HClO + H 2 O D ClO - + H 3 O + HS - + H 2 O D H 2 S + OH - HPO H 2 O D H 2 PO OH - HPO H 2 O D PO H 3 O + An amphoteric compound is able to act as either an acid or a base. Which compounds in the above equations are amphoteric?