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CH302 Chapter 7 notes part 2

# CH302 Chapter 7 notes part 2 - M acetic acid we looked at...

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CH302 Chapter 7 notes part 2 ACIDS and BASES pH of a WEAK Acid In solution we have two potential acids: HA (aq) H + (aq) + A - (aq) H 2 O (l) H + (aq) + OH - (aq) BOTH species can provide H + but K w is often MUCH smaller than K a so we assume HA is the strongest acid. [ ][ ] [ ] HA A O H K 3 a + = Example: Finding pH for a Weak Monoprotic Acid Calculate the concentrations of the various species in 0.15 M acetic acid, CH 3 COOH, solution. Percent Dissociation Percent 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 M solution of a weak monoprotic acid, HY, the acid is 5.0% ionized. Calculate K a for this acid. Using Ka to get pH, the % dissociation: The pH of a 0.10 M solution of a weak monoprotic acid, HA, is found to be 2.97. What is the value for K a ? What is the percent ionization?

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