Question

You mix 5.00 mL of 1.0x10^-5 M AgNO3 with 10.00 mL of 2.00 M NH3 solution resulting in the formation of diamminesiler(I) complex ion, [Ag(NH3)2]. (Assume volumes are additive).

a. Write the net-ionic equilibrium equation for the formation of this complex ion.

b. Calculate the concentration of the complex ion in the reaction mixture, assuming the reaction goes to completion.

Answer 1

a)

AgNO3 +2NH3 = Ag(NH3)2+ + NO3-

net ionic

Ag+(aq) + 2NH3(aq) = Ag(NH3)2+(aq)

b)

Ksp = [Ag(NH3)2+(aq)] / ([Ag+][NH3]^2)

Vtotal = 5+10 = 15 mL

[Ag+] = M1*V1/(V) = (5*10^-5)/(15) = 3.33*10^-6

[NH3] = M2V2/V = 10*2/15 = 1.333

cleraly, there is excess ammonia

copmlex assume it goes to 100%

mmol of Ag+ = MV = (3.33*10^-6) * 15 = 0.00004995

1 mmol of Ag+ = 1 mmol of copmlex

0.00004995 mmol --> 0.00004995 mmol of complex

[Ag(NH3)2] = 0.00004995 /15 = 0.00000333 M forms