Qualitative Analysis of Metal Cations? 1. a) What species are presentin a 3.0 M NH3 solution? b) Qualitatively, what is the pH of this solution? c) What reaction(s) might occur when this solution is added to a solution containing Mn2+? d) What effect will adding HNO3 to the solution from part c have? Write any chemical equations that explain your answer.
Explanation / Answer
3M NH3 --> 3M NH4+ + 3M OH- pH = 14 - pOH Kb of NH3 = 1.8x10^-5 so Ka of NH4+ = 5.56x10^-10 Kb = [NH3][H+] / [NH3] 5.56x10^-10 = x^2 / 3-x.....we can ignore x in the denominator because Kb [Mn(NH3)6] 2- adding HNO3 to [Mn(NH3)6] 2- will dissolve the complext ion HNO3 + [Mn(NH3)6] 2- --> [Mn(NH3)6](NO3)2(aq) highly soluble