Acids and Bases

Acids and Bases We encounter acids and bases everyday

Acids and Bases Acids (taste sour) Bases (taste bitter, feel slippery) flavorings (citrus, vinegar) household products (plastic, detergent, batteries) acid rain Bases (taste bitter, feel slippery) soaps antacid (tums, rolaids)

Acid Reactions Acids react with metals to produce hydrogen gas Zn(s) + 2HCl(aq)  ZnCl2(aq) + H2(g)

Acid Reactions Acids react with metal carbonates and hydrogen carbonates to produce carbon dioxide NaHCO3(s) + HC2H3O2(aq)  NaC2H3O2(aq) + H2O(l) + CO2(g) geologists can identify a rock as limestone by putting a few drops of hydrochloric acid on it and watching for bubbles of carbon dioxide to form

Identifying Acids or Bases litmus is a dye that can distinguish solutions of acids and bases aqueous solutions of acids turn blue litmus paper pink aqueous base solutions turn red litmus paper blue

Identifying Acids or Bases Acids and bases also conduct electricity That makes them electrolytes

What makes a solution acidic or basic? Why are some things acidic and some things are basic? The relative concentrations of: hydrogen ions [H+] hydroxide ions [OH-]

[H+] and [OH-] If [H+] is greater than [OH-], its an acid If [H+] is less than [OH-], its a base If [H+] =[OH-], its neither-its neutral

[H+] and [OH-] The solvent for acids and bases is usually water When water ionizes it forms equal amounts of H+ and OH- H2O  H+ + OH- Since [H+] = [OH-], water is neutral

Arrhenius Acid and Bases Arrhenius was a Swedish chemist (1883) that wondered how aqueous solutions became acidic or basic. An acid is a substance containing hydrogen that ionizes in water to produce H+ ions in solution HCl(g) + H2O  H3O+(aq) + Cl- (aq)

Vocabulary Word Arrhenius acid: a substance containing hydrogen that ionizes in water to produce H+ ions in solution

Arrhenius Acid and Bases base: substance containing a hydroxide group (OH-) that dissociates to produce OH- ions in solution NaOH(s) + H2O  Na+(aq) + OH-(aq)

Vocabulary Word Arrhenius base: substance containing a hydroxide group (OH-) that dissociates to produce OH- ions in solution

Problem Not all bases contain OH- groups

Revised Model In 1923 Bronsted (a Danish scientist) and Lowry (a British scientist) independently proposed a model that focuses on H+ ions Bronsted-Lowry model acids are H+ donors bases are H+ acceptors.

Vocabulary Word Bronsted-Lowry acid: H+ donor Bronsted-Lowry base: H+ acceptor

Bronsted-Lowry Acids and Bases HX + H2O  H3O+ + X- acid base conjugate conjugate acid base The reaction in both directions involves an acid and a base The base becomes the conjugate acid after it receives the proton The acid becomes the conjugate base after it donates the proton

Vocabulary Words conjugate acid: the species produced when a base accepts a hydrogen ion from an acid conjugate base: the species produced when an acid donates a hydrogen ion to a base

Acid Base Reactions acid base conj. acid conj. base Every Bronsted-Lowry interaction involves conjugate acid-base pairs Identify the acid, base, conjugate acid and conjugate base: acid base conj. acid conj. base

Bronsted-Lowry Bases Ammonia is a base according to the Bronsted-Lowry model, because it can accept a hydrogen ion

Identify the Species conj. base conj. acid acid base conj. acid water can be an acid or a base so it’s amphoteric