acids and bases suroviec spring 2014 chapter 15. i. definitions of acids/bases a. arrhenius acid:...
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Acids and BasesSuroviec
Spring 2014
Chapter 15
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 equilibriumWater ionization constant
Kw = 1.00 X 10-14 at 25.0oC
II. Water Ionization
C. pH scale• One way to describe the concentration of H+ in solution
or the acidity of the solution
D. Determining [H3O+] and [OH-]
pH = 1.00 pH = 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
B. Bases
C. Compare Acid/Base strength
Look at the pKa value and compare to the acid strength
D. Relationship between Ka, Kb and Kw
As acid strength increases Ka increasesAs base strength increases Kb increasesConsider the relation between a conjugate
acid-base pair HB (aq) ⇌ H+ (aq) + B- (aq) KI= Ka of HB
B- (aq) + H2O ⇌ HB (aq) + OH- (aq) KII = Kb of B-
III. Acid/Base reactions
A. Strong Acid/Strong Base
B. Strong – Weak
V. Equilibrium Calculations
A. Determining K from pH
0.015 M HOCN has a pH of 2.67, what is the [H3O+]? What is the Ka 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 Ka of 4.0 x 10-9 what are the equilibrium concentrations of HA, A-, H3O+
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 H2O 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 2.0×10-3M solution of Cod in water.
VI. Polyprotic Acids
Acids capable of donating more than 1 proton
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