Chapter 19: Acids/Bases Properties of an Acid: 1. Taste sour or tart 2. Electrolytic in solution (will conduct electricity when dissociated): a. strong acid = strong electrolyte b. weak acid = weak electrolyte 3. React w/ metal produces H 2 4. Reacts w/ OH for neutralization

Properties of Bases: 1. Feels slippery like soaps 2. Taste bitter 3. Electrolytes in solution a. strong bases = strong electrolyte b. weak bases = weak electrolyte 4. Reacts w/ acids to neutralize

Types of Acids/Bases Lewis Acid: Accepts an electron pair. Lewis Base: Donates an electron pair. Bronsted/Lowery Acid: proton donor (H + ) Bronsted/Lowery Base: proton acceptor (H + ) *Arrhenius Acids: contain hydrogens and produces H + *Arrhenius Base: produces hydroxide ions (OH - )

Naming Acids 1. Binary Acids: formed by the bonding of a hydrogen to a simple anion (Cl -, F -, S 2- ) hydro - root - ic HCl - hydro chlor ic (hydrochloric acid) HBr - hydro brom ic(hydrobromic acid) H 2 S - hydro sulfur ic (hydrosulfuric acid)

2. Ternary Acids: formed by the bonding of H + to a polyatomic ion -ate -ic, ite -ous (NEVER A HYDRO-) HNO 2 : NO 2 is nitrite, so the root is nitr- ending in -ous. Nitrous acid H 3 PO 4 : PO 4 is phosphate, so the root is phosphor- ending in -ic. Phosphoric acid Use your reference page for the anion roots!

Practice Problems Name or write the formula for the following 1. Acetic acid2. Cyanic acid 3. Nitric acid4. Hydroiodic acid 5. Boric acid6. Sulfuric acid 7. HBr8. H 2 SO 4 9. H 2 CO HF

Naming Bases Bases are compounds the produce hydroxide ions (OH - ) when dissolved in water. Element name then hydroxide NaOH : Sodium hydroxide Fe(OH) 3 : Iron (III) hydroxide

Bases CuOH : Copper (I) hydroxide Cu(OH) 2 : Copper (II) hydroxide

Strength of Acids and Bases The strength of an acid or base is defined by the dissociation of the acid or base. Strong Acids and Base = 100% dissociation Weaker Acids and Bases = less than 100% *there are therefore degrees of weak defined by a ratio of dissociation, Ka & Kb. Concentration defines strength. How is concentration expressed?

Molarity Molarity: expression of concentration. Molarity = # of moles of solute # of liters of solution M = moles/liter 1. What is the molarity of 3.65 g of HCl dissolved to a volume of 2 L? *Convert mass to moles *Calculate the molarity

Molarity: Sample Problems 1. What is the molarity of a solution of sulfuric acid when g of sulfuric acid is dissolved in 250 ml of water? 2. What mass of barium hydroxide is needed to make 2.5 L of a 0.06 molar solution? 3. What is the molarity of a solution made from 9.94 g of CoSO 4 and 250 ml of water? 4. How many grams of AgF are needed to make 500-ml of a 1.5 M solution?

Auto-ionization/Self-ionization Refers to the breakdown of H 2 O to ions. H 2 O  H + + OH - Chcts: 1. reversible 2. neutral state = 50/50 ratio 3. K w ionization product constant of water.

Other than Water If the concentration of H + is greater than OH-, then the solution is acidic. [H + ] > [OH - ]  acidic solution If the concentration of H+ is less than OH -, then the solution is basic [H + ] < [OH - ]  basic solution

The pH Scale A.pH Scale: a scale relative to the [H+] to [OH-]. 1. Scale: Basic Neutral Acidic 2. pH = -log [H + ] 3. pOH = -log [OH - ]

pH Problems 1.[H + ] : 6.5 x = pH of ___________ 2. [H + ] : 6.8 x = [OH - ] ___________ 3. pH = is a [H + ] = _______________ 4. What is the pOH of problem #3. _______ 5. pOH = 8.992, what is the pH : _________ 6. [H + ] is 3.7 x 10 -6, what is the pH: ______ 7. What is the [OH - ] in #6

4. Chstc: a. pH + pOH = 14 b. K w = [H + ] x [OH - ] (add exponents) c. [H + ] = inv log or antilog -pH d. [OH - ] = inv log or antilog -pOH 5. Indicators: substances that change color in the present of an acid or base.

Acid/Base Strengths A.Keq: Equilibrium rate constant for a reaction. Describes a point of equilibrium for a reaction. 1. Depends on solubility. See table. a. Greater solubility = stronger solution b. K eq = [product(s)] / [reactant(s)] HCl + H 2 O  H 3 O + + Cl -

K a : Acid Dissociation Constant K a = [Product (s)] / [Reactant(s)] 4HCl + O 2  2Cl 2 + 2H 2 O 1.Chcts: a. concentrations raise to the power of the coefficient in a balanced equation. b. Smaller the K a the weaker the acid c. Large K a means large dissociation.

Kb : Base Dissociation Constant K b = [Product(s)] / [Reactant(s) ] KOH  K + + OH - 1.Chstc: a. Smaller K b = weaker bases b. Large K b means large dissociation. Table 19.5 and 19.6 pages 557 and 558.

Ka and Kb Sampler Calculate the Ka from pH: 1. Write the balanced equation. 2. Write the Ka or Kb expression. 3. Use the given pH to find [H+]. 4. Distribute the [ ] & subtract from the initial [ ]. The pH of a 0.2 M HC 2 H 3 O 2 is What is the Ka for acetic acid?

Practice Problems 1. Given a 0.1 M solution of sulfurous acid with a pH of 1.48, calculate the Ka. 2.A 0.2 M solution of benzoic acid, C 6 H 5 COOH has a pH of What is the Ka ? 3.A basic solution with a pH of 12.5 has a concentration of 0.25 M BOH. What is the Kb?

Calculating pH from Ka or Kb 1.Write a balanced equation. 2.Write the Ka or Kb expression. 3.Use the equation diagram to define ‘x’. 4.Using the given Ka (Kb), insert ‘x’ for [H+] and [A-]. 5.Eliminate ‘x’ in the denominator. 6.Solve for ‘x’ 7.Calculate pH or pOH

Calculate pH from Ka/Kb 1.A given 0.15 M solution of nitrous acid, HNO 2, has a Ka = 3.45 x What is the pH? 2.A solution of 0.2 M, CsOH, has a Kb = 1.25 x What is the pH ? 3.A solution is prepared by adding 56.3 g of HCl and 62.1 g of NaOH to enough water to make 250 ml. Determine the pH of the solution?

Titration Titration is a process by which a solution of known concentration is used to determine the concentration of an unknown solution. Indicators: Chemicals that are effected by pH and used to determine the equivalent point. Equivalent Point: point of neutralization. The pH at this point depends on the strength of the acids/base involved.

Calculating Process to determine the [ ] of an unknown solution from a known solution. Setup ? pH meter Indicators: changes end-point End-point: indicates pH range via indicator Equivalent point (ovhd) mole H + = moles OH - Buffer :reduce change in pH. Hold pH steady

Buffer Capacity: amount of acid/base that can be absorbed before change in pH increase [ ] = increase in capacity Buffers contain common ions or weak acids and their conjugate base. What is the buffer for the reaction: HCN  H + + CN - Ans: any salt that contained CN - that will reverse the reaction thereby reducing H +

Calculations with titration Find the [ ] of an unknown by titration It takes 26.4 ml of 0.25 M HBr solution to neutralize 30 ml of CsOH. Find [ ] 1.Write a balanced equation 2.Convert ml  L  given [ ]  mole ratio  [?] ans: 0.22 M CsOH

What is the [ ] of nitric acid if ml of a 0.1 M KOH is neutralize 20 ml of HNO 3 ? 1.Balance the equation. 2.Convert ml  L  given [ ]  mole ratio  [ ] 3. Use [ ] to calculate pH. Textbook: p621 #32-33 ; p631 #72-80 p 632 #93-96

Sampler 1.What is the concentration of a household ammonia solution if 4909 ml 0.59 M HCl is required to neutralize 25 ml solution? 2.In a titration, ml M rubifium hydroxide solution is required to exactly neutralize 20 ml of HF acid solution. What is the molarity of HF ?