Question

can someone please show me the full reaction (i.e step wise) when Cu 2+ aqueous is slowly being added with NH3 until excess. please show me how the light blue ppt is formed and subsequently the dark blue solution.

Answer 1

When copper is reacted with ammonia, you get a complex coordinate complex, \([Cu(NH_3)_4]^{2+}\) which is the light blue that you're referring to. According to your stoichiometric equation, \(Cu^{2+}~_{(aq)} + 4 NH_3~_{(aq)} \rightarrow [Cu(NH_3)_4]^{2+}~_{(aq)}\)

Answer 2

sorry but i need to know the step wise reaction

Answer 3

so i formed Cu(H2O)4(OH)2 which is my light blue ppt. what is the reaction next if my light blue ppt react with excess ammonia?

Answer 4

i know Cu(NH3)4(H2O) 2+ forms but how? and whats the full eqn?

Answer 5

its a distorted octahedral structure, the water has a coordinate bond which is longer than the NH3 dative covalent bond

Answer 6

I think the water is an intermediate, but water isn't a very strong bonding molecule, which is where you get the release to get the tertiaryamine complex.

Answer 7

yea but im used to writing out the h2o.. so how do i get my dark blue solution from my light blue ppt?

Answer 8

I don't think you can form an octahedral species with copper.

Answer 9

I gotta step out for a bit, if someone else hasnt helped you then i will when i get back.

Answer 10

http://www.chemguide.co.uk/inorganic/complexions/ligandexch.html

Answer 11

Just do it one at a time

[Cu(H2O)4]^2+ + NH3 <-> [Cu(NH3)(H2O)3]^2+

[Cu(NH3)(H2O)3]^2+ + NH3 <-> [Cu(NH3)2(H2O)2]^2+

Answer 12

i'm not sure at what point the ppt is formed

Answer 13

Yes, at some point, the reaction is reversible.

Answer 14

hmmm ok thx!