Chapter 10 Acids Bases Characteristics of Acids sour
Chapter 10 Acids & Bases Characteristics of Acids sour p. H < 7 litmus turns red Characteristics of Bases bitter slippery p. H > 7 litmus turns blue
Arrhenius Theory of Acids/Bases HCl HBr HNO 3 H 2 SO 4 H 2 CO 3 H 3 PO 4 HCl. O 4 HC 2 H 3 O 2 An Acid is a Hydrogen-containing substance that dissociates in water to produce H+ ions. HCl H+ + Cl-
Arrhenius Theory of Acids/Bases A Base is a Hydroxide-containing substance that dissociates in water to produce OH- ions. Na. OH Na+ + OHNa. OH KOH Ca(OH)2 Al(OH)3
Bronsted Lowry Theory of Acids/Bases An Acid is a proton donor: HF + H 2 O H 3 O + + F net result: h[H 3 O + ] A Base is a proton acceptor: NH 3 + H 2 O NH 4 + + OHnet result: h[OH - ]
Conjugate Acid-Base Pairs differ by one proton A weak acid is in equilibrium with its conjugate base A weak base is in equilibrium with its conjugate acid
Mono-, Di-, & Tri-protic Acids HC 2 H 3 O 2 + H 2 O 1. H 2 CO 3 2. 1. 2. 3. H 3 PO 4
Acid/Base Strength A strong acid is 100% dissociated in aqueous solution: HCl + H 2 O H 3 O + + Cl- HBr HNO 3 A weak acid transfers only a small percentage of its acidic hydrogens to water: H 2 CO 3 + H 2 O H 3 O + + HCO 3 H 3 PO 4
Acid/Base Strength A strong base is 100% dissociated in aqueous solution: Na. OH OH - + Na+ KOH all strong bases are metal hydroxides Li. OH, Na. OH, KOH, Ba(OH)2 A weak base is only partially ionized in solution: NH 3 + H 2 O NH 4+ + OHCH 3 NH 2
HF + H 2 O acid ionization constant F - + H 3 O + Ka NH 3 + H 2 O base ionization constant = NH 4+ + OH- Kb =
Write an equation for the dissociation of the following weak acids in water: H 2 CO 3 + H 2 O HCN + H 2 O HC 2 H 3 O 2 + H 2 O Identify the conjugate acid/base pairs in the above equations. Write the Ka expression for the dissociation of the following weak acids in water. Rank the 3 acids as weak, weaker, weakest.
Acid Strong Acids: HCl, HBr, HI, HNO 3, H 2 SO 4, HCl. O 4 Weak Acids: H 3 PO 4 HF HC 2 H 3 O 2 H 2 CO 3 HCN Conjugate Base
Amphiprotic Substances: Water can act as an acid or a base: H 2 O + H 2 O Write the equilibrium constant expression:
In a neutral solution: [H 3 O+] = [OH-] = 1 x 10 -7 M The Ion Product Constant for Water: Kw = a. A solution of hydrochloric acid has a hydronium ion concentration of 1. 5 x 10 -3 M. What is the hydroxide ion concentration? b. What is the hydronium ion concentration in a 6. 0 x 10 -4 M Na. OH solution?
p. H is a measure of the acidity (or basicity) of an aqueous solution p. H = -log[H 3 O+] A logarithm (base 10) is the exponent by which the base must be raised in order to obtain the number. Example: find the p. H of a solution in which [H 3 O+] = 1 x 10 -3 M
Acidic p. H < 7 p. H = p. OH = 7 neutral in any solution: Kw = [H 3 O+] [OH-] and: p. Kw = p. H + p. OH = 14 Basic p. H > 7 (the log of a product is equal to the sum of the logs of each factor)
Fill in the Table (integer values of p. H & p. OH): [H 3 O+]p. H [OH-] p. OH A/B/N? 1 x 10 -5 M 10 1 x 10 -3 M 1 N
Calculating p. H with noninteger numbers : Find the p. H of a solution that has [H 3 O+] = 6. 5 x 10 -5 M p. H = -log[6. 5 x 10 -5 ] = use the log button on your calculator Calculating [H 3 O+] from p. H (noninteger numbers): If the p. H of a solution is 9. 53, what is the [H 3 O+]? [H 3 O+] = 10 -p. H = use the 10 x button on your calculator
p. H [H 3 O+] 6. 3 x 10 -3 4. 82 3. 9 x 10 -8 8. 20 2. 6 x 10 -12
Fill in the Table (record p. H & p. OH to 2 decimal places): [H 3 O+]p. H 6. 7 x 10 -5 M [OH-] p. OH A/B/N? 2. 38 4. 5 x 10 -3 M 5. 11
Weak Acids: Ka H 3 PO 4 7. 5 x 10 -3 HF 6. 8 x 10 -4 HC 2 H 3 O 2 1. 8 x 10 -5 H 2 CO 3 4. 3 x 10 -7 HCN 4. 9 x 10 -10 K p a
Hydrolysis of Salts: Salts are products of the reaction between acids & bases HF + Na. OH Na. F + H 2 O The salt of a weak acid and a strong base hydrolyzes to produce a basic solution. Na. F + H 2 O
Hydrolysis of Salts: Salts are products of the reaction between acids & bases HCl + NH 3 NH 4 Cl + H 2 O The salt of a weak base and a strong acid hydrolyzes to produce an acidic solution. NH 4 Cl + H 2 O
HCl + Na. OH Na. Cl + H 2 O The salt of a strong base and a strong acid does not undergo hydrolysis Na. Cl + H 2 O The salt of a weak base and a weak acid will produce a weakly acidic or basic solution (depending on the relative strengths of the conjugate acid & base) NH 4 F + H 2 O
Buffer Solutions: A solution that contains both a weak acid and a weak base is a Buffer • Minimizes changes in p. H • Absorbs small quantities of added H 3 O+ or OHConsider a solution that contains both HF and F 1. When a strong acid is added: 2. When a strong base is added:
Conjugate acid/base pairs commonly used as buffers HC 2 H 3 O 2/C 2 H 3 O 2 H 2 PO 4 -/HPO 42 H 2 CO 3/HCO 3 HA/A- Ka p. Ka
Determining the p. H of a Buffer Write an equation for the dissociation of a generic weak acid, HA, in water: HA + H 2 O Ka = Take the -log of both sides of the expression: Solve for p. H=
Henderson-Hasselbalch Equation: a Find the p. H of an acetic acid/acetate buffer if: [HC 2 H 3 O 2] = 0. 10 M [C 2 H 3 O 2 -] = 0. 10 M Ka = 1. 8 x 10 -5
Henderson-Hasselbalch Equation: a Find the p. H of an acetic acid/acetate buffer if: [HC 2 H 3 O 2] = 0. 10 M [C 2 H 3 O 2 -] = 0. 25 M Ka = 1. 8 x 10 -5
A buffer solution is prepared with the following concentrations of carbonic acid and sodium bicarbonate. 1. Write an equation for the dissociation of carbonic acid in water. 2. Calculate the p. H of the buffer. [H 2 CO 3] = 1. 0 M [HCO 3 -] = 0. 10 M Ka = 4. 3 x 10 -7
Find the p. H of a solution that is 0. 024 M in bicarbonate ion and 0. 0020 M in carbonic acid. H 2 O + H 2 CO 3 H 3 O+ + HCO 3 - Find the p. H of a solution that is 0. 024 M in bicarbonate ion and 0. 0030 M in carbonic acid.
Control of Blood p. H: Normal [H 2 CO 3] = 2. 4 mmol/Liter H 2 CO 3 Normal p. H = 7. 35 – 7. 45 Normal [HCO 3 -] = 22 -30 mmol/Liter H 3 O+ + HCO 3 - [H 2 CO 3] regulated by dissolved CO 2 + H 2 O [CO 2] regulated by respiration Normal p. CO 2 = 40 mm Hg Acidosis = increased [H 3 O+] due to: diabetic ketoacidosis, aspirin overdose, restricted breathing (emphysema), lactic acid from exercise, etc. Alkalosis = decreased [H 3 O+] due to: hyperventilation, drug overdose, prolonged vomiting (loss of stomach acid)
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