gardul
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Ammonia and tap water
Okay i was doing a test run on my setup for purifying NH3. When I noticed a white precipitate forming at the bottom as it cooled.
Here is the set up.
1000ml E. flask with Stopper. a glass tube and a hose connecting to a 250ml E. flask and that goes into another 500ml flask filled with
H2O. I only used Tap water for the test and not distilled. So I'm just wondering if any of you might know what it might be. I have city
water if that helps.
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HgDinis25
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I don't know If I understood correctly what you described. You bubbled Ammonia gas through water to purify it? First, what are the impurities? Second,
ammonia is quite soluble in water. Third, this won't give you anhydrous ammonia gas.
So, when you bubble Ammonia through water, an ionization happens:
NH3(g) <--> NH3(aq)
NH3(aq) + H2O(l) <--> NH4+(aq) + HO-(aq)
Tap water usually contains Calcium ions dissolved. The harder the water the more Calcium ions it contais. When the Hydroxide ions form (reaction
above) they combine with the Calcium ions present to form Calcium Hydroxide:
2HO-(aq) + Ca+(aq) --> Ca(OH)2(s)
This is only one explanation to what might happen. However, there are ways to confirm it. Retrieve your precipitate by filtration or decant the
liquid. Then, add HCl and see if the precipitate reacts. There should be no liberation of CO2. If it does dissolve away it's most likely Calcium
Hydroxide. Tap water may also contain other ions, like Magnesium, that would also form insoluble hydroxides.
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DraconicAcid
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Calcium hydroxide is pretty soluble; magnesium hydroxide or calcium carbonate is more likely.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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gardul
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I bubbled ammonia in water to purify the ammonia.
I don't know the impurities in the water. The ammonia has lemon sent in it that is for one thing.
Sorry if i'm not making much sense. Ive had a long day and am tired.
I know Ammonia is soluble in water it was what was going for to get a better product.
I just was wondering if anyone you knew what might be in city water . I found it rather intresting that I got something out of a test run and just
making sure everything will be working correctly. Just surprised me that is all.
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HgDinis25
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@DraconicAcid
Calcium Hydroxide has a solubility in water of 0,173/100mL at 20ºC. But yes, within the rather insoluble ones, Calcium Hydroxide is pretty soluble
Anyway, this all comes down to a few tests that can me made to the precipitate. In half a liter of water there's probably not enough Calcium ions to
make enough Calcium Hydroxide to produce a precipitate, like DraconicAcid said. Magnesium Hydroxide isn't the most plausible possibilty either,
because city water doesn't have that much magnesium.
I didn't consider this, but calcium carbonate may indeed be your precipitate.
When Ammonia is added, this happens:
NH3(g) <--> NH3(aq)
NH3(aq) + H2O(l) <--> NH4+(aq) + HO-(aq)
However, Calcium Bicarbonate dissolved in the water (this is what makes hard water so evil  ) exists as an equilibrium:
Ca(HCO3)2 <--> CaCO3(s) + H2CO3
Carbonic Acid (almost not present because the equilibrium constant is quite low and any formed would decompose) ionizates:
H2CO3(aq) + 2H2O(l) <--> 2H3O(aq) + CO3-(aq)
The Hydoxide ions formed in the ionization of the Ammonia would react with the Hydronium ions formed in the ionization of the Carbonic Acid:
HO-(aq) + H3O+(aq) --> 2H2O(l)
This would consume the Hydronium ions, shifting the Carbonic Acid equilibrium to the right. Thus, the conentration of Carbonic acid would decrease,
shifting the Calcium Bicarbonate equilibrium to the right, forming Calcium Carbonate. The Ammonium ions (from the Ammonia ionization) and the
Carbonate ions (from the Carbonic Acid ionization) would maintain the electroneutrality of the solution.
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subsecret
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If you washed with a small amount of water, the solution would become saturated with ammonia quickly enough for most of it to pass through. Are you
trying to get anhydrous ammonia or an ammonia solution?
Fear is what you get when caution wasn't enough.
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Random
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How much precipitate is there? By the way as it's already said probably some alkaline earth. If it's not it would be a huge concern. But white color,
probably alkaline earth.
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gardul
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Awesomeness - Since my local store only had ammonia in lemon sent, I needed to get rid of it. so an ammonia solution would be the answer.
Random- about 2 grams from a 250ml of tap water. It is white and dried rather quickly. I havn't done any further tests on it. as I am working on other
things.
I would really like to see if i can get more of this unknown when I am done with these and expierment to see if i can really pin point what it is.
When I did use distilled water nothing precipitated
it was just unextecting and rather intresting.
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dermolotov
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Quote: Originally posted by gardul  | | Awesomeness - Since my local store only had ammonia in lemon sent, I needed to get rid of it. so an ammonia solution would be the answer.
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There's a pretty high chance that the lemon might not be that soluble in water.
...is the rest of the gas coming off devoid of scents? That's not a sure-fire tell but it's a start.
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