Special Conditions for Buffers

Special Conditions [weak acid] = [weak base] Then pH = pKa At equivalence point( moles H+ = moles OH-) Weak acid plus a strong base (1 liter) HA + OH-  H2O + A- .1 mol .1 mol 0 mol -.1 mol -.1 mol + .1 mol 0 mol 0 mol .1 mol A- is weak base, therefore you will need to solve a weak base problem. A- + H2O  HA + OH-

Titration Titration: A method of determining the concentration of a solution. Titration Curve: Shows pH change Equivalence point: moles acid = moles base End point: when the indicator changes color

Titration Curves Strong Acid with a Strong Base HCl + NaOH  H2O + NaCl Overall solution at eq point has a pH of 7 pH 7 Eq point Vol SB

Titration of a Weak Acid with Strong Base Why is the pH Above 7? HA + OH-  H2O + A- We made a weak base. Weak base dissociates to make a basic solution. A- + H2O  HA + OH- pH Eq point 7 Vol SB

Titration of WB with a SA Why is pH below 7? A- + H+  HA We made a weak acid. So then the weak acid will dissociate, making the solution acidic. HA  H+ + A- pH 7 Eq point Vol SA