Lecture 162/28/05 4:30 TODAY Dr. William Shay TSC 006

Sulfanilic acid, which is used in making dyes is made by reacting aniline with sulfuric acid. The acid has a pK a value of The sodium salt of the acid is quite soluble in water. If you dissolve 1.25 g of the salt in 125 mL of solution, what is the pH of the solution?

What is a buffer? HA + H 2 O ↔ H 3 O + + A -

pH of a buffer system What is the pH of a buffer that is 0.12 M lactic acid HC 3 H 5 O 3 and 0.1 M sodium lactate? K a = 1.4 x 10 -4

pH with Henderson-Hasselbach What is the pH of a buffer that is 0.12 M lactic acid HC 3 H 5 O 3 and 0.1 M sodium lactate? K a = 1.4 x 10 -4

Addition of strong acid/strong base Always a 2 step process: Neutralization (100% completion) Equilibrium

A buffer is prepared by mixing 0.15 mol of lactic acid and 0.2 mol of sodium lactate and raised to 1 L with water. K a = 1.4 x a) pH = ? b) pH after adding 0.05 mol HCl c) pH after adding 0.1 mol NaOH