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38 since both 10 3 rules apply the henderson

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Unformatted text preview: nce both “10-3 rules” apply, the Henderson-Hasselbalch equation can be used. 12.01 Chem 321 Quiz 2 3. (8) Name Answer Key Use activities to calculate the pH of a 0.10 M aqueous solution of KCN. initial CN- + H2O 0.10 M Kb º HCN + OH- equil (0.10 - x) ~ 0.10 0 x ~10-7 M let x = increase in [HCN] (10-7 + x) ~ x assumes 10-7<< x << 0.1 since KCN is a +1,-1 electrolyte, μ = 0.10 M and γOH- = 0.76 γCN- = 0.755 γHCN = 1 Substituting into the above equation yields: Note that both assumptions are valid. pOH = -log aOH- = -log [OH-]γOH- = -log (1.26 x 10-3)(0.76) = 3.02 pH = 14 - pOH = 10.98 10.98...
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This document was uploaded on 03/06/2014 for the course CHEM 321 at CSU Northridge.

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