Acids and Bases Chapter 14 Sections 1-3, 11

Acid – produce Hydrogen ions in aqueous solution Base – produce hydroxide ions in aqueous solution Arrhenius Acid and Base Bronsted-Lowry Acid and Base Acid – proton donor Base – proton acceptor Conjugate Acid-Base pairs – two chemicals that differ by a hydrogen ion, p + HA (aq) + H 2 O (l)  H 3 O + (aq) + A - (aq) Acid dissociation constant, Ka Write the dissociation equation for the following acids (without water) HCl  HC 2 H 3 O 2  NH 4 +  C 6 H 5 NH 3 +  [Al(H 2 O) 6 ] 3+ 

Acid – electron pair acceptor has an empty atomic orbital that can share an electron pair Base – electron pair donor has an electron pair to share with another molecule Let’s draw some structures BF 3 + NH 3  BF 3 NH 3 Al 3+ + H 2 O  [Al(OH) 6 ] 3+ Aluminum accepts one electron pair from each of the water molecules SO 3 + H 2 O  H 2 SO 4 Lewis Acid-Base Model

Identify the Lewis acids and bases Ni NH 3  [Ni(NH 3 ) 6 ] 2+ H + + H 2 O  H 3 O + Lewis Acid-Base Model

Comparing the Acid Base Definitions

Strong Acid – the equilibrium lies far to the right A strong acid yields a weak conjugate base (a low affinity for a proton) Weak acid – the equilibrium lies far to the left The weaker the acid the stronger its conjugate base. Acid Strength

Various Ways to Describe Acid Strenth

Values of Ka for Some Common Monoprotic Acids

H 2 O, F -, Cl -, NO 2 -, CN - Arrange according to their strengths as bases

What is a … diprotic acid? oxyacid? organic acid? carboxyl group monoprotic acid? amphoteric substance? Definitions

The autoionization of water H 2 O (l) + H 2 O (l)  H 3 O + (aq) + OH - (aq) Ion product constant or dissociation constant for water K w = [H + ] [OH - ] = 1 x A neutral solution, where [H + ] = [OH - ] A basic solution, where [OH - ] > [H + ] An acidic solution, where [H + ] > [OH - ] Kw

At 60  C, the value of Kw is 1.0 x Using LeChatelier’s principle, predict whether the reaction 2H 2 O (l)  H 3 O + (aq) + OH - (aq) is exothermic or endothermic. Calculate the [H + ] and [OH - ] in a neutral solution at 60  C Kw

Calculate the [H + ] of each of the following solutions at 25 °C. Identify each solution as neutral, acidic, or basic. a.[OH - ] = 1.5 M b.[OH] = 3.6 x M Kw

pH = - log [H + ] Sig. Figs: The number of decimal places in the log is equal to the number of significant figures in the original number [H + ] = 1.0 x pH = 9.00 pOH = - log [OH-] pH + pOH = 14 pK = -log K pK w = -logK w = 14 pK w = pH + pOH = 14 pH Page 632

The pH of gastric juice in a person’s stomach is 2.1. Calculate the pOH, [H + ], and [OH - ] for this sample. Is gastric juice acidic or basic? pH Page 632

Calculate [OH - ], [H + ], pH, and pOH for each of the following: a M Ca(OH) 2 b.A solution containing 25 grams of KOH per liter c.A solution containing grams of NaOH per liter pH Page 632