Acid-Base Reactions Ch 17.6
What kind of reactions are possible? • There are 4 types: • Strong Acid/ Strong Base • Strong Acid/ Weak Base • Weak Acid/ Strong Base • Weak Acid/ Weak Base = no fun
Strong Acid and Strong Base • It is easy since it is 100% Ionized • The Net Ionic is just the hydronium ion with the hydroxide ion to make water • Very Large K Value = All product (for all practical purposes.
Strong acid is completely ionized in solution to form hydronium ion The hydronium ion reacts with the OH ions from the weak base. Ex: HCl and Ammonia Large K value = goes essentially to completion NH4+ is the conjugate acid of a weak base so it creates an Acid in water. Strong Acid w/ a Weak Base
Important Ideas here! • Mixing equal molar quantities of a strong acid and a weak base produces an acidic solution • The overall reaction is the reverse that defines Ka for the conjugate acid of the weak base, so the overall K is 1/ Ka. NH4+ ‘s Ka = 5.6 X 10-10 so Knet = 1/(5.6 X 10-10 ) = 1.8 X 109
Weak Acid with a Strong Base • Take every thing we said and reverse it • Ti esrever dna dias ew gniht yreve ekat • Equal molar quantities makes a basic solution • The conjugate base of the weak acid’s Kb is related to the Knet = 1/Kb
Weak Acid with a Weak Base • If they are equal volumes, look at the relative Ka and Kb’s to determine • Acetic acid mixed with ammonia
Solving for the pH of an Acid base solution • If you add 50mL of 0.10M NaOH with exactly 50mL of 0.1M formic acid HCO2H. What is the pH of the resulting solution? Kb is 5.6 X 10-11 • Step 1: Do the Stoich • Calculate the quantity of base added, quantity of acid consumed, and the quantity of conj base formed • Step 2: Calc concentrations Calculate the conc of conj base (VOLUMES ARE ADDITIVE) • Find pH using Kb of cong base