Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: VenDiddy on May 09, 2005, 07:24:14 PM
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Question:
Excess concentrated aqueous ammonia is added to solid silver chloride.
Answer:
AgCl + NH3 => Ag(NH3)2+1 + Cl-
Can someone please explain why this works? ???
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By the way, I believe it forms Ag(NH3)2+1, not +2. Sorry, but all I know is that it forms, not how. However, I think it may have to do with the N from the NH3 (which is slightly negative) being attracted to the Ag+1 ion.
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Just corrected the charge. Chemistry baffles me...
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i also asked a similar question last time, its just that it forms a complex salt . as for why it forms a complex salt... well maybe ammonia could be more concentrated and hence displaces chlorine and forms the unstable salt with silver... just my thoughts
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and hence displaces chlorine and forms the unstable salt with silver... just my thoughts
Silver cholride itself is insoluble in water, though is ionic in solid state.
After addition of ammnia complex Ag+ forms complex cation Ag(NH3)2+i and this new compund
Ag(NH3)2+Cl- is soluble in water.
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AgCl is VERY slightly solube in water (But it's such a small solubility number that we basically just say 'it's insoluble'). So by removing the Ag+ ions from the water, you shift the equillibrium which allows more AgCl to dissolve, so more Ag+ is formed which is then eaten up again, etc. etc.
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1. AgCl (s) <-> Ag+ (aq) + Cl- (aq)
2. Ag+ + 2NH3 <-> Ag(NH3)2+
equilibirum 2 has a very high Kstability constant. effectively, adding concentrated ammonia removes Ag+ in solution because Ag+ is converted to another form. This favours the forward reaction (Le Chatelier's Principle) of Equlibrium 1. The net effect is AgCl exhibits higher solubility in concentrated ammonia.