Presentation on theme: "ACIDS AND BASES SUROVIEC SPRING 2014 Chapter 15. I. Definitions of Acids/Bases A. Arrhenius Acid: something that releases H + in water Base: something."— Presentation transcript:
I. Definitions of Acids/Bases A. Arrhenius Acid: something that releases H + in water Base: something that releases OH - in water B. Brønsted-Lowry Acid: substance that donates a proton Base: substance that accepts a proton
C.Monoprotic vs. Polyprotic Monoprotic acid – only has 1 proton to donate base – only can accept 1 proton Polyprotic acid – can donate several protons Base – can accept several protons
D.Conjugate Acid-Base Pairs A pair of compounds that differ by the presence of one H + is called a conjugate acid-base pair Every reaction between a Brønsted acid and Brønsted base involves H + transfer and has 2 conjugate acid-base pairs
II. Water Ionization A. Water equilibrium Water ionization constant K w = 1.00 X 10 -14 at 25.0 o C
II. Water Ionization C. pH scale One way to describe the concentration of H + in solution or the acidity of the solution
D. Determining [H 3 O + ] and [OH - ] pH = 1.00pH = 10.50
IV. Equilibrium constants A. Acid Acids and bases are either: strong electrolytes: completely dissociates weak electrolytes: ionizes very little in water Ionization constants measure extent of ionization: K>1: ionize extensively, strong acid/base K<1: does not ionize extensively, weak acid/base
C. Compare Acid/Base strength Look at the pKa value and compare to the acid strength
D. Relationship between K a, K b and K w As acid strength increases Ka increases As base strength increases Kb increases Consider the relation between a conjugate acid-base pair HB (aq) ⇌ H + (aq) + B - (aq) K I = K a of HB B - (aq) + H 2 O ⇌ HB (aq) + OH - (aq) K II = K b of B -
III. Acid/Base reactions A. Strong Acid/Strong Base
V. Equilibrium Calculations A. Determining K from pH 0.015 M HOCN has a pH of 2.67, what is the [H 3 O + ]? What is the K a of HOCN?
B. Determining the Equilibrium Concentrations and pH from Ka A. Weak acid ionization Given a weak acid (HA) concentration of 0.040M with a K a of 4.0 x 10 -9 what are the equilibrium concentrations of HA, A -, H 3 O +
C. 5% rule Codeine (Cod) is a powerful and addictive painkiller. It is also a weak base. Write the reaction of weak base Cod with H 2 O If the Ka of Hcod (the weak conjugate acid) is 1.2×10 -8, what is the Kb of Cod? Find the pH of a 2.0×10 -3 M solution of Cod in water.
VI. Polyprotic Acids Acids capable of donating more than 1 proton