Question

Given that

Ka for HCN is 4.9×10−10 and

Kb for NH3 is 1.8×10−5 ,

calculate

Kb for CN− and

Ka for NH4+ .

Enter the Kb value for CN− followed by the Ka value for NH4+ , separated by a comma, using two significant figures.

Answer 1

Ka for HCN is 4.9×10−10

   HCN -------------> CN^-

acid                        conjugate base

Kb   = Kw/Ka

       = 1*10^-14/4.9*10^-10

       = 2.1*10^-5

Kb for NH3 is 1.8×10−5

       NH3 -------------------> NH4^+

    base                              conjugate acid

     Ka   = Kw/Kb

             = 1*10^-14/1.8*10^-5

             = 5.6*10^-10 >>>>.answer