Chapter 18 ACIDS & BASES Honors Chemistry

Acids and Bases are necessary in the production of many industrial goods. They are also commonly used in many household products. Section 18.1 Introduction to Acids and Bases

Properties of Acids Acids taste sour. Acids are conductors of electricity. Most acids are corrosive. Acids can neutralize bases. Sulfuric and Nitric acids cause damage in acid rain. Acids turn blue litmus red.

Properties of Bases Bases taste bitter and feel slippery. Bases are also conductors of electricity. Strong bases can burn your skin. Bases can neutralize acids. Many detergents and cleaning solutions are basic. Bases turn red litmus blue. Acids and Bases

Properties of Acids and Bases All water solutions contain hydrogen ions (H + ) and hydroxide ions (OH – ). An acidic solution contains more hydrogen ions than hydroxide ions.acidic solution A basic solution contains more hydroxide ions than hydrogen ions.basic solution

The usual solvent for acids and bases is water— water produces equal numbers of hydrogen and hydroxide ions in a process called self- ionization. H 2 O (l) + H 2 O (l) ↔ H 3 O + (aq) + OH – (aq) The hydronium ion is H 3 O +.

The Arrhenius Model ArrheniusArrhenius acid is a substance that contains hydrogen and ionizes to produce hydrogen ions, H +, in solutions. HCl ionizes to produce H + ions. HCl (g) → H + (aq) + Cl - (aq)

The Arrhenius Model Arrhenius base is a substance that contains a hydroxide group and dissociates to produce a hydroxide ion, OH -, in solution. NaOH dissociates to produce OH - ions. NaOH (s) → Na + (aq) + OH - (aq)

Section 18.2 Strengths of Acids and Bases Strengths of Acids Acids that ionize completely are strong acids.strong acids Strong acids produce more H + ions in solution than weak acids. Because they produce the maximum number of hydrogen ions, strong acids are good conductors of electricity. Acids that ionize only partially in dilute aqueous solutions are called weak acids.weak acids

Strengths of Bases A base that dissociates completely into metal ions and hydroxide ions is known as a strong base.strong base Strong bases produce more OH - ions than weak bases. A weak base dissociates only partially in dilute aqueous solution.weak base

Section 18.3 Hydrogen Ions and pH Ion Product Constant for Water Pure water contains equal concentrations of H + and OH – ions and is neutral. The ion production of water, K w = [H + ][OH – ]. The ion product constant for water is the value of the equilibrium constant expression for the self-ionization of water.ion product constant for water

Ion Product Constant for Water With pure water at 298 K, both [H + ] and [OH – ] are equal to 1.0 × 10 –7 M. K w at 298 K = 1.0 × 10 – x = [H + ] [OH - ]

pH and pOH pH is the negative logarithm of the hydrogen ion concentration of a solution.pH pH = –log [H + ]

pH and pOH pOH of a solution is the negative logarithm of the hydroxide ion concentration.pOH pOH = –log [OH – ] 14 = pH + pOH

Determining [H + ] & [OH - ] If pH or pOH is given, it is possible to determine the [H + ] & [OH - ]. [H + ] = inv log (-pH) [OH - ] = inv log (-pOH)

Section 18.4 Neutralization Reactions Between Acids and Bases A neutralization reaction is a reaction in which an acid and a base in an aqueous solution react to produce a salt and water.neutralization reaction A salt is an ionic compound made up of a cation from a base and an anion from an acid.salt Acid + Base  salt + H 2 O HCl + NaOH  NaCl + H 2 O

Titration is a method for determining the concentration of a solution by reacting a known volume of that solution with a solution of known concentration.Titration In a titration procedure, a measured volume of an acid or base of unknown concentration is placed in a flask, and initial pH recorded. A buret is filled with the titrating solution of known concentration, called a titrant.titrant

Measured volumes of the standard solution are added slowly and mixed into the solution in the flask and the pH is measured. The process continues until the reaction reaches the equivalence point, which is the point at which moles of H + ion from the acid equals moles of OH – ion from the base.equivalence point An abrupt change in pH occurs at the equivalence point.

Chemical dyes whose color are affected by acidic and basic solutions are called acid-base indicators. acid-base indicators An end point is the point at which an indicator used in a titration changes color.end point An indicator will change color at the equivalence point. Titration Video

Indicator Chart

Practical Applications of Acids & Bases Neutralization has many practical applications. Reclamation (restoration) of land once used for mining also involves neutralization reactions. Neutralization is also used to deal with environmental problems. Acids and bases are used in the manufacture of fertilizers, synthetic fabrics, pigments, petroleum, iron and steel, explosives, dyes, plastics, pesticides, soaps and detergents, paper, film, and many other chemicals.

They are also used for various other purposes, including cleaning surfaces, refining oil and sugar, electroplating metals, and treating food products. Sulfuric acid is the chemical most widely used in industry. Nitric acid, another important industrial acid, is used in the manufacture of fertilizers, plastics, photographic film, and dyes and explosives as dynamite and TNT.

Hydrochloric acid is used to clean metals, brick and tile; it is used in the manufacture of sugar and glue. pH plays an important role in the chemistry of the body. Softening of water using soda lime process by municipalities and wastewater treatment.