1 / 14

CHAPTER 16: (HOLT) ACID-BASE TITRATION AND pH

CHAPTER 16: (HOLT) ACID-BASE TITRATION AND pH. I. Concentration Units for Acids and Bases. A. Chemical Equivalents 1. Definition: quantities of solutes that have equivalent combining capacity

wauna
Télécharger la présentation

CHAPTER 16: (HOLT) ACID-BASE TITRATION AND pH

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CHAPTER 16: (HOLT)ACID-BASE TITRATION AND pH

  2. I. Concentration Units for Acids and Bases • A. Chemical Equivalents • 1. Definition: quantities of solutes that have equivalent combining capacity • a. Acid: mass of one equivalent is numerically equal to the mass of one mole of the acid divided by the number of protons(H+ or H3O +) that one mole of the acid can provide • Example: • HCl 36 g/mol; 1 eq = 1H +; 36 g/mol H + • H2SO4 98g/mol; 2 eq = 2H +; 49 g/mol H +

  3. B. Base: mass of one equivalent is numerically equal to the mass of one mole of the base divided by the number of protons(OH-) that one mole of the base can provide • Example: • NaOH 40 g/mol; 1 eq = 1 OH-; 40 g/mol OH- • Ca(OH)2 74 g/mol; 2 eq = 2 OH-; 37 g/mol OH-

  4. B. Normality • Definition: number of equivalents of solute per liter of solution • N = eq of solute • L of solution

  5. C. Relationship Between Normality and Molarity • N = nM • N: Normality • n: number of equivalents (# of H+= or OH-) • M: Molarity • Example: • 1M HCl = 1N HCl 1M NaOH = 1N NaOH • 1M H2SO4 = 2N H2SO4 1M Ca(OH)2 = 2N Ca(OH)2

  6. II. Aqueous Solutions and the Concept of pH • A. Self-Ionization of Water • 1. Definition: Two water molecules interact to produce a hydronium ion and a hydroxide ion by proton transfer - forms a weak electrolyte • 2. [ ] is symbol used to indicate concentration in moles per liter (Molarity) • 3. H2O + H2O <---> H3O+ + OH- ; • in pure water [H3O+ ] = [OH- ] • 4. [H3O+ ][OH- ] = 10-14 • 5. If the [H3O+ ] increases then the [OH- ] decreases or • If the [H3O+ ] decreases then the [OH- ] increases

  7. B. The pH scale • 1. pH -- the negative of the common logarithm of the hydronium ion concentration • pH = -log[H3O+ ] • 2. Acid: pH < 7 • 3. Base: pH > 7 • 4. Neutral: pH = 7

  8. C. Calculations involving pH • pH = -log[H3O+ ] • 0.001 M HCl = [H3O+ ] =1 x 10 -3 • pH = -log[1 x 10-3] • pH = 3 (acid) • {Remember that [H3O+ ][OH- ] = 1 x 10-14 ; so if [H3O+ ] = 1 x 10-3; then [OH- ] = 1 x 10-11 • FYI: there is also pOH = - log[OH- ] and • pH + pOH = 14

  9. III. Acid-Base Titrations • A. Indicators • 1. Definitions: • a. indicators - weak acid or base dyes whose colors are sensitive to pH, or hydronium, concentration • b. transition interval - the pH range over which an indicator changes color

  10. 2. Types of indicators • a. Change color at about pH 7 • b. Change color below pH 7 • c. Change color above pH 7

  11. B. The Principle of Titration • Definitions: • 1. Titration - the controlled addition and measurement of the amount of a solution of known concentration that is required to react completely with a measured amount of a solution of unknown concentration • 2.Standard solution - a solution that contains a precisely known concentration of a solute

  12. 3. Equivalence point - in a neutralization reaction, the point at which there are equivalent quantities of hydronium and hydroxide ions • 4. End point - the point in a titration where an indicator changes color • 5. Primary standard - a highly purified compound, when used in solution to check the concentration of the known solution in a titration

  13. C. Molarity and Titration • 1. Determine the moles of acid (or base) from the standard solution used during titration • 2. From a balanced chemical equation, determine the ratio of moles of acid (base) to base (acid) • 3. Determine the moles of solute of the unknown solution used during the titration • 4. Determine the molarity of the unknown solution

  14. D. Normality and Titrations • Va x Na = Vb x Nb • Va : volume of the acid • Na : normality of the acid • Vb: volume of the base • Nb: normality of the base

More Related