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Title: What concentration of ammonia, [NH3], should be present in a solution with [NH4+] = 0.809 M to produce a buf? Post by: nylande on Apr 15, 2013 What concentration of ammonia, [NH3], should be present in a solution with [NH4+] = 0.809 M to produce a buffer solution with pH = 9.59? For NH3, Kb = 1.8E-5.
Title: What concentration of ammonia, [NH3], should be present in a solution with [NH4+] = 0.809 M to produce a buf? Post by: fierce_eagle on Apr 15, 2013 pH = pKa + log (base/acid)
Title: What concentration of ammonia, [NH3], should be present in a solution with [NH4+] = 0.809 M to produce a buf? Post by: smith332306 on Apr 15, 2013 Using the Henderson-Hasselbalch Equation:
pH = pKa + log (base/acid) pH = pKa + log ([NH3]/[NH4+]) Kb(NH3) x Ka(NH4+) = Kw 1.8 x 10^-5 x Ka(NH4+) = 1.0 x 10^-14 Ka(NH4+) = 1.0 x 10^-14 / 1.8 x 10^-5 = 5.56 x 10^-10 pKa = - log Ka = - log (5.56 x 10^-10) = 9.26 pH = pKa + log ([NH3]/[NH4+]) 9.59 = 9.26 + log ([NH3] / 0.809) 0.33 = log ([NH3] / 0.809) 0.33 = log [NH3] - log 0.809 0.33 = log [NH3] + 0.09 log [NH3] = 0.33 - 0.09 = 0.24 [NH3] = 10^0.24 = 1.74 M |