Chapter 7 Acids and Bases

Arrhenius Definitions － Acids produce hydrogen ion in aqueous, and bases produce hydroxide ions. Brønsted-Lowry Definitions － An acid is a proton (H + ) donor, and a base is a proton acceptor. Lewis Acid-Base Definitions － An acid as an electron pair acceptor and a base as an electron donor.

An Acid is Dissolved in Water acidbase conjugate acid conjugate base

Conjugate Acid-Base Pair Conjugate acid-base pair consists of two substances related to each other by the donating and accepting of a single proton.

Water as an Acid and a Base Water is the common amphoteric substance. K w =[H 3 O + ][OH - ]=1× ion-product constant pH=-log[H + ]

Calculating the pH of Weak Acid Solutions 1.0M Before 0 0 Equilibrium (1-x)MxMxMxMxM

The 5% Rule The validity of an approximation should always be check. The 5% rule should be used to evaluate which approximation are reasonable. The approximation is acceptable.

The pH of a Mixture of Weak Acids HNO 2 is assumed to be the dominant producer of H +.

x xx

Percent Dissociation xxx

Polyprotic Acids Diprotic Acids

The Concentration of Species of Polyprotic Acid As a Function of pH

Polyprotic Acid － H 3 PO 4

Calculate the equilibrium concentration of the different species in a 0.1 M phosphoric acid solution at pH=3.

Acid-Base Properties of Salts Salt that produce neutral solutions Salts that consist of the cations of strong bases and the anions of strong acids have no effect on [H + ] when dissolved in water. The aqueous solutions of salts such as KCl, NaCl, NaNO 3 and KNO 3 are neutral.

Acid-Base Properties of Salts Salt that produce basic solutions

Acid-Base Properties of Salts Salt that produce acidic solutions

Water Contributes to the Very Dilute H + Concentration

If [H + ] 2 >>K w, the full equation reduces to the typical expression for a weak acid.