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Why is ammoniacal silver nitrate brown? :confused:

Present in the ammoniacal solution of silver nitrate:
NaOH
AgNO3
NH4OH
Which does not explain the colour and so I cannot concentrate to read on:mad:
Why?
Book: This solution is made by adding a few drops of dilute sodium hydroxide to a solution of silver nitrate followed by dilute ammonia solution until the brown precipitate dissolves.:confused: :confused:
Reply 1
Avatar for ssadi
ssadi
OP
1
ssadi
Present in the ammoniacal solution of silver nitrate:
NaOH
AgNO3
NH4OH
Which does not explain the colour and so I cannot concentrate to read on:mad:
Why?
Book: This solution is made by adding a few drops of dilute sodium hydroxide to a solution of silver nitrate followed by dilute ammonia solution until the brown precipitate dissolves.:confused: :confused:

I forgot to add, to accentuate my point, that NaOH, AgNO3 and NH4OH are all colourless. I just don't understand how they are mixed up to get brown.
im no expert but colour arises to the the different groups absorb/reflet/emit different wavelengths of light. I suppose this is a form of spectroscopy.

Im assuming that the groups in ammonical silver nitrate just happen to absorb lots of colourless and emit to colour brown
Reply 3
Avatar for shengoc
shengoc
12
ssadi
Present in the ammoniacal solution of silver nitrate:
NaOH
AgNO3
NH4OH
Which does not explain the colour and so I cannot concentrate to read on:mad:
Why?
Book: This solution is made by adding a few drops of dilute sodium hydroxide to a solution of silver nitrate followed by dilute ammonia solution until the brown precipitate dissolves.:confused: :confused:


In the visible light spectrum, there are seven colours, all the other colours we see are the combinations of two or more of these colours. Suppose brown is made of colours A and B, then in the spectrum, A and B must have not been absorbed, so you are left with A and B which give you the colour brown.
ssadi
Present in the ammoniacal solution of silver nitrate:
NaOH
AgNO3
NH4OH
Which does not explain the colour and so I cannot concentrate to read on:mad:
Why?
Book: This solution is made by adding a few drops of dilute sodium hydroxide to a solution of silver nitrate followed by dilute ammonia solution until the brown precipitate dissolves.:confused: :confused:


There is no mystery here..

when sodium hydroxide is added to a solution of silver ions a precipitate of silver oxide appears - This is light brown. (in common with many solids, the reasons for the colour are complex)

When you add ammonia solution to this ppt it redissolves as the diammine complex.
Reply 5
Avatar for ssadi
ssadi
OP
1
charco
There is no mystery here..

when sodium hydroxide is added to a solution of silver ions a precipitate of silver oxide appears - This is light brown. (in common with many solids, the reasons for the colour are complex)

When you add ammonia solution to this ppt it redissolves as the diammine complex.

Thanks
I thought I figured it out yesterday, thought AgOH forms. :biggrin:
it is AgO that went brown

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