Arrhenius Definition of

Arrhenius Definition of • Acids • Bases - Substances that produce hydrogen ions, H+ when dissolved in water HCl  H+ + Cl- - Substances that produce hydroxide ions, OH- when dissolved in water NaOH  Na+ + OH-

What is ammonia? NH3 Acid or base?

Bronsted-Lowry Definition of - Any substance in a chemical reaction that donates H+ ( a proton) • Acids • Bases HCl + H2O  H3O+ + Cl- Hydronium ion - Any substance in a chemical reaction that accepts H+ (a proton) NH3 + H2O ↔ NH4+ + OH-

NH3 + H2O ↔ NH4+ + OH- • Reversible reaction indicates products reform reactants • Base does not completely ionize • Base is weak • Can look at the reaction in reverse

Acetic acid, HC2H3O2, is a weak acid • Write a reaction to describe its dissociation • Label the acid, base, conjugate acid and conjugate base

Naming • What are some acids (names/formulas)? 1. Name: HBr, KOH, NH3, Al(OH)3, H2SO3, H2SO4, H3PO4, H2S, CU(OH)2 2. Write formulas for: nitrous acid, barium hydroxide, hydrofluoric acid, nitric acid, ammonia, silver hydroxide, acetic acid

H H H H-N: + H-O: <-> H-N-H + :O-H H H Lewis Definition of - Any substance in a chemical reaction that accepts an electron pair • Acids • Bases - Any substance in a chemical reaction that donates an electron pair NH3 + H2O ↔ NH4+ + OH- + - : : :

Do now • Name NaOH, HClO, HC2H3O2, NH3 • Write formulas for sulfuric acid, nitric acid, potassium hydroxide

Complete this reaction H3O+(aq) + OH-(aq) H2O(l) + H2O(l) <-> For any aqueous solution!!! Acid Base Conj. Acid Conj. Base Kw = [H3O+][OH-] = 1 x 10-14 (at 25ºC) In pure water, at 25ºC, what would the hydronium and hydroxide ion concentrations be??? [H3O+] = [OH-] = 1x10-7 M

Find the hydronium ion concentration for eggs whose hydroxide ion concentration is 1.6x10-8 M. Is this sample acidic or basic? • What is the hydroxide ion concentration for a soft drink whose hydronium ion concentration is 5.8 x 10-4M. Is this solution acidic or basic?

Do Now: • What is the hydronium ion? How does it relate to the hydroxide ion concentration? • Find the hydronium ion concentration of a cleaning product whose hydroxide ion concentration is 0.054 M • What is … 102? 103? 10-1? 10-4? • What power is ten raised to… to get 10? 100? 0.1? 0.01? 10-7? • Tell me everything you know about pH.

What is pH? • pH = -log [H3O+] • What is the pH of pure water at 25ºC whose hydronium ion concentration is 1x10-7 M • What is the pH of a cleaning product whose hydroxide ion concentration is 1x10-3M? Is it acidic or basic?

Do now • What is pH? • What does it measure? How do we find it? What does it tell us? • What is pOH? How does it relate to pH? • What differentiates a strong acid from a weak acid?

Kw = [H3O+][OH-]= 1x10-14pH =-log[H3O+]pOH = -log[OH-] pH + pOH = ? 14 10 –pH = [ H3O+]

Write a reaction for the dissociation • Does it dissociate completely or reversibly? • Use stoichiometry to relate concentration of reactants and products. What is the pH of a 1.0 M HCl solution? What is the pH of a 1.0 M HC2H3O2 solution?

What is the pH of a 1.0 M Sr(OH)2 solution? What is the pH of a 1.0 M HC2H3O2 solution? What is the pH of a 1.0 M NH3 solution? What is the concentration of all species present in the above solutions?

DO NOW: What is the pH of a 1.0 M Sr(OH)2 solution? What is the concentration of all species present in the above solutions? What is the concentration of all species present in a 1.0 M ammonia solution? What is the pH?

Strong acids??? Strong bases??? HCl, HBr, HI, HNO3, HClO4, H2SO4 Group I and II metal hydroxides Polyprotic Acid

Do Now • What is a pH indicator? • What is the pH of a 0.1 M HCl solution? • What is the pH of a 0.01 M NaOH solution? • What is the concentration of a solution prepared by taking 1 mL of 0.01 M NaOH and dissolving it in sufficient water to create 10 mL of solution?

What is a pH indicator? • Chemical compounds that are added to a solution so the pH can easily be determined • Weak organic acid and its conjugate base • Acid represented by HIn (to simplify) • Write a dissociation reaction for the “acid”, HIn HIn + H2O <-> In- + H3O+ Color 1Color 2

Phenolphthalein, C20H14O4

Do Now: • A solution has a pH of 4.5. Is it acidic or basic? What is the hydronium ion concentration? • How are hydronium and hydroxide ion concentrations related? • How do you calculate pH and pOH and how are they related? • How do you determine the pH of a strong acid or base? Describe the steps. • How do you determine the pH of a weak acid or base? Describe the steps.

What is a salt? • Crystalline compound composed of the negative ion of the acid and the positive ion of the base NaCl Neutral Salt NaOH HCl Strong Strong Base Acid

Ammonium Chloride • Write the formula of this salt • Identify the parent acid and base that produced this salt • Is this salt acidic, basic, or neutral? • If so, which part of this salt acts as the acid or base? Write a hydrolysis reaction for the acidic or basic ion. (hydrolysis = put it in water)

Sodium Acetate • Write the formula of this salt • Identify the parent acid and base that produced this salt • Is this salt acidic, basic, or neutral? • If so, which part of this salt acts as the acid or base? Write a hydrolysis reaction for the acidic or basic ion

What is a buffer? • A buffered solution resists a change in pH • What must it be made of? Weak acid and its salt or a weak base and its salt Contain relatively large concentrations of weak acid and corresponding weak base. Works as long as concentrations of buffering materials are large compared to amount of H+ or OH- added.

What is an Acid-Base Titration? • Laboratory technique to determine the concentration of acid or base • React a solution whose concentration you know (Standard) with a solution whose concentration is unknown • Example: Standard is 1.25 M HCl solution, NaOH solution concentration is unknown. Write a reaction for this neutralization.

Beaker contains 50.0 mL of 1.25 M HCl and a few drops of phenolphthalein • Slowly start adding the base, NaOH, whose concentration is unknown • Eventually will reach the equivalence point moles H+ = moles OH- Do you know that you have reached the equivalence point? Go one drop past, and now solution is basic - You have reached the endpoint Buret, NaOH NO! HCl

moles H+ = moles OH- • To reach endpoint, 73.6 mL of base was required

What if acid is diprotic? • Use normality (another measure of concentration) • Normality is ratio of equivalents/liter • An equivalent is The amount of acid that will donate 1 mole H+ The amount of base that will accept 1 mole of H+ At equivalence point…mole H+ = mole OH- NaVa = NbVb

Try these! • What is the concentration (molarity and normality) of HCl if 40.0 mL is required to reached the endpoint when titrated against 85.0 mL of 0.50 M Sr(OH)2? • What is the volume of 0.75 M H2SO4 required to reach the endpoint when titrated against 300. mL of 1.25 M NH3? At what pH will the equivalence point occur?

What is the pH of 1.0 M HC2H3O2 solution? Look in your notes. • What is the effect of dissolving sodium acetate in this solution? What will happen to the pH? Common ion effect – addition of a common ion increases the concentration of one of the products thereby shifting the reaction toward the opposite side Calculate the pH of a solution that is 1.0 M acetic acid and 1.0 M sodium acetate.

Arrhenius Definition of