Chemistry Ch 19

Topics: Acid, PH, Acid dissociation constant Pages: 6 (1930 words) Published: May 28, 2013
Chapter 19 Objectives:
Upon completion the student should be able to: **Define the properties of acids and bases **Compare and contrast acids and bases as defined by the theories of Arrhenius, Bronsted-Lowry and Lewis **Write dissociation equations for both acids and bases **Define a conjugate acid and a conjugate base and know how each is formed **Describe the formation of a hydronium ion **Understand the hydrogen ion and hydroxide ion concentration as it relates to aqueous solutions **Classify a solution as an acid, base or neutral given the hydrogen ion or hydroxide ion concentration using the ion product constant for water **Know the pH scale as it relates to acids, bases and neutral solutions **Calculate pH values from hydrogen ion or hydroxide ion concentrations **Describe the purpose of an acid-base pH indicator **Define strong acids and weak acids **Calculate the Keq and the Ka constants for acid dissociation **Calculate the Keq and the Kb constants for base dissociation **Know that large Ka and Kb values signify a strong acid or base whereas small Ka and Kb values signify a weak acid or base **Write completely balanced neutralization reactions **Define the products of a neutralization reaction **Solve titration word problems

Chapter 19 Notes:
Acids and bases: Acid Characteristics: 1. 2. 3. 4. 5. Base Characteristics: 1. 2. 3. 4. 5. The Three definitions and theories of acids and bases: Arrhenius: *Acids are compounds that yield hydrogen ions in aqueous solutions *Bases are compounds that yield hydroxide ions in aqueous solutions Monoprotic acids: Diprotic acids: Triprotic acids:

example: H2SO4 , H(NO3), H3 (PO4) example: H2(SO4)(aq) ---------------> 2H+ + (SO4) -2 example: K(OH) aq) -----------------> K+ + (OH)-

Bronsted - Lowry acids and bases: *Acids are hydrogen ion donors *Bases are hydrogen ion acceptors example: NH3 + H20 NH4+ + OH-

conjugate acid: a particle formed when a base gains a hydrogen ion conjugate base: a particle that remains after an acid has donated a hydrogen ion

Note: water is amphoteric - a split personality - it can accept hydrogen ions or donate them. It can be either an acid or a base in some reactions. HCl + H20 -------------> H30+ + Lewis acids and bases: *Acids can accept a pair of electrons *Bases can donate a pair of electrons example: NH3 The self ionization of water: Water and the Hydronium ion *water is highly polar and in constant motion example: H20 + H20 -------------> H30+ + OHCl-

*The reaction in which water molecules react with one another to produce ions is called self ionization and occurs to a very small extent [H30+] or [H+] = 1.0 X 10-7 moles/liter (M) [OH-] = 1.0 X 10-7 moles/liter (M)

The ion-product constant for water: Kw = [H+] X [OH-] = 1.0 X 10-14 (moles/L)2 *The product of the hydrogen ion concentration and the hydroxide ion concentration is equal to Kw for aqueous solutions *water pulls strong acids apart (dissociation). The [H+] concentration is greater than the [OH-] concentration example: If the [H+] is 1.0 X 10-5 moles/liter, what is the [OH-] concentration? Base or Acid? The pH Scale:

**Know these four important formulas(below). These four formulas will allow you to solve for hydrogen ion concentration, hydroxide ion concentration, pH and pOH answers when given needed information. 1. Kw = [H+] X [OH-] = 1.0 X 10-14 (moles/L)2 2. pH + pOH = 14 3. pH = - log [H+] 4. pOH = -log [OH-]

example: What is the pH of a solution in which the [H+] = 1.0 X10-10 moles/liter? pH = - log (1.0 X 10-10 moles/liter) = - (log 1 + log 10-10) = - (0.0) + (-10) = 10 What is the [OH-] concentration??

example: What is the pH of a solution in which the [H+] = 2.5 X 10-4 moles/liter? pH = - log (2.5 X 10-4 moles/liter) pH = ???? What is the [OH-] concentration?? sample problem: The [OH-] concentration of a solution is 3.0 X 10-8 moles/liter, determine the pH and pOH.

Acid and base Indicators: see page 601-603 An indicator is an acid or base that...
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