19+Acids,+Bases+and+Salts

=Objectives= 19.1 19.2 19.3 19.4 19.5
 * What are the properties of acids and bases?
 * How did Arrhenius define an acid and a base?
 * What distinguishes an acid from a base in the Brønsted-Lowry theory?
 * How did Lewis define an acid and a base?
 * How are [H+ ] and [OH - ] related in an aqueous solution?
 * How is the hydrogen-ion concentration used to classify a solution as neutral, acidic, or basic?
 * What is the most important characteristic of an acid-base indicator?
 * How does the value of an acid dissociation constant relate to the strength of an acid?
 * How can you calculate an acid dissociation constant (//K//a ) of a weak acid?
 * What are the products of the reaction of an acid with a base?
 * What is the endpoint of a titration?
 * When is the solution of a salt acidic or basic?
 * What are the components of a buffer?

=Outlined Notes=

I. Acid-Base Theories A. Properties of Acids and Bases 1. Acids a. Acids taste sour, will change the color of an acid-base indicator, and can be strong or weak electrolytes in aqueous solution. 2. Bases a. Bases taste bitter, feel slippery, will change the color of an acid-base indicator, and can be strong or weak electrolytes in aqueous solution. B. Arrhenius Acids and Bases 1. Arrhenius said that acids are hydrogen-containing compounds that ionize to yield hydrogen ions (H+) in aqueous solution. He also said that bases are compounds that ionize to yield hydroxide ions (OH-) in aqueous solution. 2.Arrhenius Acids a. __monoprotic acids__- acids that contain one ionizable hydrogen b. __diprotic acids__- acids that contain two ionizable hydrogens c. __triprotic acids__- acids that contain three ionizable hydrogens C. Bronsted-Lowry Acids and Bases 1. The Bronsted-Lowry theory defines an acid as a hydrogen-ion donor, and a base as a hydrogen-ion acceptor 2. Conjugate Acids and Bases a. __conjugate acid__- particle formed when a base gains a hydrogen ion b. __conjugate base__- particle that remains when an acid has donated a hydrogen ion c. __conjugate acid__-base pair- consists of two substances related by the loss or gain of a single hydrogen bond d. __hydronium ion (H3O+)__- a water molecule that gains a hydrogen ion e. __amphoteric__- substance that can act as both an acid and a base D. Lewis Acids and Bases 1. Lewis proposed that an acid accepts a pair of electrons during a reaction, while a base donates a pair of electrons a. __Lewis acid__-substance that can accept a pair of electrons to form a covalent bond b. __Lewis base__- substance that can donate a pair of electrons to form a covalent bond

II. Hydrogen Ions and Acidity A. Hydrogen Ions from Water 1. __self-ionization__- the reaction in which water molecules produce ions 2. __neutral solution__- any aqueous solution in which (H+) and (OH-) are equal B. Ion Product Constant for Water 1. For aqueous solutions, the product of the hydrogen-ion concentration and the hydroxide-ion concentration equals 1.0 X 10^-14 a. __ion-product constant for water__-the product of the concentrations of the hydrogen ions and hydroxide ions in water b. __acidic solution__- one in which (H+) is greater than (OH-) c. __basic solution__- one in which (H+) is less than (OH-) d. __alkaline solutions__- basic solution C. The pH Concept 1. Calculating pH a. A solution in which (H+) is greater than 1 x 10^-7 M has a pH less than 7 and is acidic. The pH of pure water or a neutral aqueous solution is 7. A solution with a pH greater than 7 is basic and has a (H+) of less than 1 X 10-7 M. (1.) __pH__- is the negative logarithm of the hydrogen-ion. D. Measuring pH 1. Acid-Base Indicators a. An indicator is a valuable tool for measuring pH because its acid form and base form have different colors in solution.

III. Strengths of Acids and Bases A. Strong and Weak Acids and Bases 1. __strong acids__-completely ionized in aqueous solution 2. __weak acids__- ionize only slightly in aqueous solution 3. Acid Dissociation Constant a. Weak acids have small Ka values. The stronger an acid is, the larger its Ka value. (1.) __acid dissociation constant (Ka)__- the ratio of the concentration of the dissociated (or ionized) form of an acid to the concentration of the undissociated (nonionized) form 4. Base Dissociation Constant 1. __strong bases__- dissociate completely into metal ions and hydroxide ions in aqueous solution 2. __weak bases__- react with water to form the hydroxide ion and the conjugate acid of the base 3. __base dissociation constant (Ka)__- is the ratio of the concentration of the conjugate acid times the concentration of the hydroxide ion to the concentration of the base B. Calculating Dissociation Constants 1.To find the Ka of a weak acid or the Kb of a weak base, substitute the measured concentrations of all the substances present at equilibrium into the expression Ka or Kb.

IV. Neutralization Reactions A. Acid-Base Reactions 1. In general, the reaction of an acid with a base produces water and one of a class of compounds called salts. a. __neutralization reactions__- reactions in which an acid and a base react in an aqueous solution to produce a salt and water B. Titration 1. The point of neutralization is the end point of the titration a. __equivalence point__- when the number of moles of hydrogen ions equals the number of moles of hydroxide ions b. __titration__- process of adding a known amount of solution of known concentration to determine the concentration of another solution c. __standard solution__- solution of known concentration d. __end point__- the point at which the indicator changes color

V. Salts in Solution A. Salt Hydrolysis 1. In general, salts that produce acidic solutions contain positive ions that release protons to water. Salts that produce basic solutions contain negative ions that attract protons from water. a. __salt hydrolysis__- the cations or anions of a dissociated salt remove hydrogen ions from or donate hydrogen ions to water B. Buggers 1. A bugger is a solution of a weak acid and one of its salts, or a solution of a weak base and one of its salts a. __buffer__- solution in which the pH remains relatively constant when small amounts of acid or base are added b. __buffer capacity__- amount of acid or base that can be added to a buffer solution before a significant change in pH occurs









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