Acid-Base Reactions Ch 17.6

What kind of reactions are possible? There are 4 types: There are 4 types: Strong Acid/ Strong Base Strong Acid/ Strong Base Strong Acid/ Weak Base Strong Acid/ Weak Base Weak Acid/ Strong Base Weak Acid/ Strong Base Weak Acid/ Weak Base = no fun Weak Acid/ Weak Base = no fun

Strong Acid and Strong Base It is easy since it is 100% Ionized It is easy since it is 100% Ionized The Net Ionic is just the hydronium ion with the hydroxide ion to make water 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. Very Large K Value = All product (for all practical purposes.

Strong Acid w/ a Weak Base Strong acid is completely ionized in solution to form hydronium ion Strong acid is completely ionized in solution to form hydronium ion The hydronium ion reacts with the OH ions from the weak base. The hydronium ion reacts with the OH ions from the weak base. Ex: HCl and Ammonia Large K value = goes essentially to completion NH 4 + is the conjugate acid of a weak base so it creates an Acid in water.

Important Ideas here! Mixing equal molar quantities of a strong acid and a weak base produces an acidic solution Mixing equal molar quantities of a strong acid and a weak base produces an acidic solution The overall reaction is the reverse that defines K a for the conjugate acid of the weak base, so the overall K is 1/ K a. NH 4 + s Ka = 5.6 X so K net = 1/(5.6 X ) = 1.8 X 10 9 The overall reaction is the reverse that defines K a for the conjugate acid of the weak base, so the overall K is 1/ K a. NH 4 + s Ka = 5.6 X so K net = 1/(5.6 X ) = 1.8 X 10 9

Weak Acid with a Strong Base Take every thing we said and reverse it Take every thing we said and reverse it Ti esrever dna dias ew gniht yreve ekat Ti esrever dna dias ew gniht yreve ekat Equal molar quantities makes a basic solution Equal molar quantities makes a basic solution The conjugate base of the weak acids K b is related to the K net = 1/K b The conjugate base of the weak acids K b is related to the K net = 1/K b

Weak Acid with a Weak Base If they are equal volumes, look at the relative K a and K b s to determine If they are equal volumes, look at the relative K a and K b s to determine Acetic acid mixed with ammonia 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 HCO 2 H. What is the pH of the resulting solution? K b is 5.6 X If you add 50mL of 0.10M NaOH with exactly 50mL of 0.1M formic acid HCO 2 H. What is the pH of the resulting solution? K b is 5.6 X Step 1: Do the Stoich Step 1: Do the Stoich Calculate the quantity of base added, quantity of acid consumed, and the quantity of conj base formed Calculate the quantity of base added, quantity of acid consumed, and the quantity of conj base formed Step 2: Calc concentrations Step 2: Calc concentrations Calculate the conc of conj base (VOLUMES ARE ADDITIVE) Find pH using K b of cong base Find pH using K b of cong base