Question

I'm working on my gen chem 2's review guide and im completely unsure of how to do both of these problems. Please, help with set by set answers with some explainations would be great too!

1. A complex was formed by adding 0.15 M Ni(NO3)₂ to 2.5 M NH₃ (aq). How much Ni²⁺ remains in the solution? Show the chemical equation and the expression for any K that you use.

2. Predict the molar solubility of silver iodide in 2.2 NH₃?

Thank you for your help in advanace!!!

Answer 1

1)

K = x / (0.15-x) * (2.5-x)⁶ This is the expression for K
but to solve for remaining Ni⁺² in solution you need to substitute value of K and solve

2)
AgI <---------K_sp------> Ag⁺ + I^-
Ag⁺²+ 2NH₃ <-----K-------> Ag(NH₃)₂
NH₃+ H₂O <-------K_b-------> NH₄⁺ + OH^-
K_sp = [Ag⁺] [ I^-] ; K = [ Ag(NH₃)₂] / [Ag⁺²] [NH₃]² ; K_b = [NH₄⁺] [OH^-] / [NH₃]
Do an ICE table for  Ag(NH₃)₂ , assume all silver ions exist as Ag(NH₃)₂
s, is the molar solubility
  

K = s *s / (2.2 - 2s)²   
substitute the value of K for the reaction and solve for s