Acids and Bases!  Acids and Bases (and calculations involving them) are essential to all areas of analytical chemistry!

What are Acids/Bases?  Aqueous Definition  Brønsted-Lowry Definition  Lewis Definition

Conjugate Acids and Bases  These are the products of acid/base reactions! CH 3 C(O)OH + CH 3 NH 2  CH 3 C(O)O - + CH 3 NH 3 + Acid (H + donor) base (H + acceptor) conjugateconjugate base (lost H + ) acid (gained H + )

Acids, Bases, and Equilibrium  We can write the autoprotolysis (self-ionization) of water in this way: H 2 0 H + + OH - For this reaction, the measured K (K w ) is 1.0 x at 25° C. You can calculate initial and final concentrations of [H + ] and [OH - ] from this equation. Remember: K is temperature dependent!

pH!  pH is another way to express [H + ] in solution  pH = -log [H + ], or log 1/[H + ]  Also, pOH = -log[OH - ] or pOH =log 1/[OH - ]  A useful relation:  pH + pOH = 14 at 25°C

Strong/Weak acids and bases  Strong acids and bases:  HCl H + + Cl -  Weak acids and bases:  HA + H 2 O H 3 O + + A -  HA H + + A -

Polyprotic Acids/Bases  These compounds have the ability to donate or accept more than one proton.  Example, PO H can accept 3 protons  There’s a K for each reaction!

Example problem 1  What is the pH of a 1.8*10 -3 M solution of HCl?

Example 2  What is the pH of the resulting solution when moles of acetic acid are dissolved in water and diluted to 1.00 L? CH 3 COOH (aq)  H + (aq) + CH 3 COO - (aq) K a = 1.8x10 -5 at 25 o C.

Example 3  What is the pH of the resulting solution when moles of trichloroacetic acid are dissolved in water and diluted to 1.00 L? CCl 3 COOH (aq)  H + (aq) + CCl 3 COO - (aq) K a = 1.3x10 -1 at 25 o C.

Example 4  A M solution of the weak acid HA has a pH of Calculate pK a for HA.