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Topic: Excess concentrated aqueous ammonia is added to a solution of nickel(II)bromide.  (Read 15101 times)

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Offline mrdeadman

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Excess concentrated aqueous ammonia is added to a solution of nickel(II)bromide.
« on: May 09, 2006, 11:11:44 PM »
here's what happens: Ni 2+ + NH3 -> [Ni(NH3)6]2+
does anyone know why?
also what does sodium sulfide do in water? does it take an H+ from water forming OH-?
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Offline rctrackstar2007

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Re: Excess concentrated aqueous ammonia is added to a solution of nickel(II)bromide.
« Reply #1 on: May 09, 2006, 11:25:03 PM »
i agree. the original reactants were NiBr2 + NH3 -> ?

why would it not be something like NH3NiBr, without having dealt with sub numbers yet of course?
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The world is like an atom. The not-quite-as-intelligent people are the nucleus all packed together sharing a common...everything. We, we are the electrons. Granted we're not as smart as these engineers and what-not so we're most likely in the first orbital, but we're the electrons of this giant atom. We all have differing intelligences and ideas and we are separated from the nucleus which makes us better because no one really cares about how a nucleus acts. It's the electrons that make chemistry, except for nuclear chem, of course, which I am a big fan of.

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Offline mike

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Re: Excess concentrated aqueous ammonia is added to a solution of nickel(II)brom
« Reply #2 on: May 09, 2006, 11:26:08 PM »
You must attempt the answer for yourself first and show some work or no one will answer.
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Offline rctrackstar2007

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Re: Excess concentrated aqueous ammonia is added to a solution of nickel(II)bromide.
« Reply #3 on: May 09, 2006, 11:28:38 PM »
these are my thoughts...

it would take the H+ and make HSO4- so...

Na+ + SO42- + H2O -> HSO4- + OH-

??? maybe??
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The world is like an atom. The not-quite-as-intelligent people are the nucleus all packed together sharing a common...everything. We, we are the electrons. Granted we're not as smart as these engineers and what-not so we're most likely in the first orbital, but we're the electrons of this giant atom. We all have differing intelligences and ideas and we are separated from the nucleus which makes us better because no one really cares about how a nucleus acts. It's the electrons that make chemistry, except for nuclear chem, of course, which I am a big fan of.

-Your's truly, 2006;
  written to describe the HS chem student apart from the average being

Offline mike

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Re: Excess concentrated aqueous ammonia is added to a solution of nickel(II)brom
« Reply #4 on: May 09, 2006, 11:31:22 PM »
Firstly sodium sulfide is Na2S
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Offline mrdeadman

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Re: Excess concentrated aqueous ammonia is added to a solution of nickel(II)brom
« Reply #5 on: May 09, 2006, 11:32:04 PM »
Quote from: mike on May 09, 2006, 11:26:08 PM
You must attempt the answer for yourself first and show some work or no one will answer.
i did attempt it, but i just want to know why it does that? i could've never guessed it.
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Offline rctrackstar2007

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Re: Excess concentrated aqueous ammonia is added to a solution of nickel(II)brom
« Reply #6 on: May 09, 2006, 11:34:18 PM »
Quote from: mike on May 09, 2006, 11:31:22 PM
Firstly sodium sulfide is Na2S

my bad i read the question wrong

sorry  :-[
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The world is like an atom. The not-quite-as-intelligent people are the nucleus all packed together sharing a common...everything. We, we are the electrons. Granted we're not as smart as these engineers and what-not so we're most likely in the first orbital, but we're the electrons of this giant atom. We all have differing intelligences and ideas and we are separated from the nucleus which makes us better because no one really cares about how a nucleus acts. It's the electrons that make chemistry, except for nuclear chem, of course, which I am a big fan of.

-Your's truly, 2006;
  written to describe the HS chem student apart from the average being

Offline rctrackstar2007

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Re: Excess concentrated aqueous ammonia is added to a solution of nickel(II)bromide.
« Reply #7 on: May 09, 2006, 11:37:07 PM »
it comes out as sulfur being a spectator ion. why does this happen mike or whoever reads this one?
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AP Chemistry Squad Member [002]

The world is like an atom. The not-quite-as-intelligent people are the nucleus all packed together sharing a common...everything. We, we are the electrons. Granted we're not as smart as these engineers and what-not so we're most likely in the first orbital, but we're the electrons of this giant atom. We all have differing intelligences and ideas and we are separated from the nucleus which makes us better because no one really cares about how a nucleus acts. It's the electrons that make chemistry, except for nuclear chem, of course, which I am a big fan of.

-Your's truly, 2006;
  written to describe the HS chem student apart from the average being

Offline Borek

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Re: Excess concentrated aqueous ammonia is added to a solution of nickel(II)bromide.
« Reply #8 on: May 10, 2006, 03:45:49 AM »
Quote from: rctrackstar2007 on May 09, 2006, 11:37:07 PM
it comes out as sulfur being a spectator ion. why does this happen mike or whoever reads this one?

No. S2- is a strong Bronsted base. It reacts with water leaving OH- and HS-.
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Offline Will

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Re: Excess concentrated aqueous ammonia is added to a solution of nickel(II)bromide.
« Reply #9 on: May 10, 2006, 07:34:29 AM »
Quote from: mrdeadman on May 09, 2006, 11:11:44 PM
here's what happens: Ni2+ + 6NH3  -> [Ni(NH3)6]2+
does anyone know why?

When NiBr2 is dissolved in water, [Ni(H2O)6]2+ is formed. This is important to remember because then you can work out what happens when different solutions are added.
NH3 is a better ligand than H2O because the lone pair on NH3 has more electron density than the lone pair in H2O (because nitrogen is less electronegative than oxygen, so it 'holds on' to its' electrons less than oxygen). Therefore Ni2+ can be better stabilised by ammonia ligands than water ligands. Hence, ligand exchange will occur and all the H2O ligands will be replaced by NH3 ligands when conc. ammonia is added forming [Ni(NH3)6]2+ + 6H2O.

Quote from: mrdeadman on May 09, 2006, 11:11:44 PM
also what does sodium sulfide do in water? does it take an H+ from water forming OH-?

I would've thought it just dissolves. But if I were you, I'd believe Borek more than me! ;D
« Last Edit: May 10, 2006, 07:51:48 AM by will17 »
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Offline mrdeadman

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Re: Excess concentrated aqueous ammonia is added to a solution of nickel(II)bromide.
« Reply #10 on: May 10, 2006, 08:21:46 AM »
Quote from: will17 on May 10, 2006, 07:34:29 AM
When NiBr2 is dissolved in water, [Ni(H2O)6]2+ is formed. This is important to remember because then you can work out what happens when different solutions are added.
NH3 is a better ligand than H2O because the lone pair on NH3 has more electron density than the lone pair in H2O (because nitrogen is less electronegative than oxygen, so it 'holds on' to its' electrons less than oxygen). Therefore Ni2+ can be better stabilised by ammonia ligands than water ligands. Hence, ligand exchange will occur and all the H2O ligands will be replaced by NH3 ligands when conc. ammonia is added forming [Ni(NH3)6]2+ + 6H2O.
thanks! that is exactly what i was looking for.
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