Question

Q1)What is the common ion in a solution that is saturated with the salts Na3PO4, Na2SO4, and AgCl?

Ag+, Na+, po4^3-, so4^2-, cl-

Q2What is the pH of a buffer made by adding 50.0mL of 0.200M HCl to 100.0mL of 0.400M NH3? pKa(NH4+)=9.26.

Do NOT use scientific notation!

Answer 1

Q1    Na2SO4 --------. 2Na⁺ + So4^2-

      Na3PO4 --------->3Na⁺ + Po4^3-

      AgCl ---------. Ag⁺ + Cl^-

Ag+, Na+, po4^3-, so4^2-, cl-

Q2    NH3 + HCl ----------> NH4Cl

no of moles of HCl = molarity * volume in L

                              = 0.2*0.05 = 0.01 moles

no of moles of NH3   = 0.4*0.1 = 0.04 moles

                NH3 +   HCl ----------> NH4Cl

I                 0.04     0.01                 0

C              -0.01    -0.01               0.01

E              0.03      0                   0.01

       Pkb = 14-PKa

               = 14-9.26   = 4.74

     POH   = PKb + log[NH4Cl]/[NH3]

              = 4.74 + log0.01/0.03

              = 4.74-0.4771

               = 4.2629