CH302 Chapter 7 notes part 2 ACIDS and BASES pH of a WEAK AcidIn solution we have two potential acids: HA(aq)↔H+(aq)+ A-(aq) H2O(l)↔H+(aq)+ OH-(aq) BOTH species can provide H+but Kwis often MUCH smaller than Kaso we assume HA is the strongest acid. HAAOHK3a−+=Example: Finding pH for a Weak Monoprotic Acid Calculate the concentrations of the various species in 0.15 Macetic acid, CH3COOH, solution. Percent DissociationPercent Dissociation = amount dissociated(mol/L)x 100% initial concentration(mol/L) Another way to see how strong an acid is. A STRONG acid will be 100% dissociated. Example: In a 0.12 Msolution of a weak monoprotic acid, HY, the acid is 5.0% ionized. Calculate Kafor this acid. Using Ka to get pH, the % dissociation: The pH of a 0.10 Msolution of a weak monoprotic acid, HA, is found to be 2.97. What is the value for Ka? What is the percent ionization?
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