AcidBase Reactions

1
Acid-Base Reactions

• Ch 17.6

2
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

3
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.

4
Strong Acid w/ a Weak Base

• 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.

5
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

6
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 acids Kb is
  related to the Knet 1/Kb

7
Weak Acid with a Weak Base

• If they are equal volumes, look at the relative
  Ka and Kbs to determine
• Acetic acid mixed with ammonia

8
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