Common ways of making Ammonia in the lab ?
The most obvious is reacting a strong alkali with an ammonium salt.
Are there any others ?
What would happen if I heated SOLID CaO and NH4Cl ?
Are there any others ?
What would happen if I heated SOLID CaO and NH4Cl ?
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Original post by Ari Ben Canaan
The most obvious is reacting a strong alkali with an ammonium salt.
Are there any others ?
What would happen if I heated SOLID CaO and NH4Cl ?
Are there any others ?
What would happen if I heated SOLID CaO and NH4Cl ?
The standard method to prepare ammonia is solid calcium hydroxide and ammonium chloride. However, I imagine that it would also work with calcium oxide.
It is one of the few reactions where two solids are reacted together on heating. The reason it 'works' is that the ammonium chloride tends to dissociate into ammonia and hydrogen chloride on heating and the HCl can then attack the base leaving the ammonia behind...
react solid calcium hydroxide and ammonium chloride... GOt this in an exam once... 
Original post by charco
The standard method to prepare ammonia is solid calcium hydroxide and ammonium chloride. However, I imagine that it would also work with calcium oxide.
It is one of the few reactions where two solids are reacted together on heating. The reason it 'works' is that the ammonium chloride tends to dissociate into ammonia and hydrogen chloride on heating and the HCl can then attack the base leaving the ammonia behind...
It is one of the few reactions where two solids are reacted together on heating. The reason it 'works' is that the ammonium chloride tends to dissociate into ammonia and hydrogen chloride on heating and the HCl can then attack the base leaving the ammonia behind...
One other question.
During a chemistry practical I have noticed that in some tests that I observe fizzing upon adding HCl.
Usually this means the presence of a carbonate ion.
However, the examiner's report often states that it is necessary to test the evolved gas with limewater.
How would I do this ? Usually I am carrying the test out in a small test tube and I am never provided with a gas syringe, connecting tubes or other apparatus.
So it is a logistics issue of getting the gas into a small amount of limewater.
Original post by Ari Ben Canaan
One other question.
During a chemistry practical I have noticed that in some tests that I observe fizzing upon adding HCl.
Usually this means the presence of a carbonate ion.
However, the examiner's report often states that it is necessary to test the evolved gas with limewater.
How would I do this ? Usually I am carrying the test out in a small test tube and I am never provided with a gas syringe, connecting tubes or other apparatus.
So it is a logistics issue of getting the gas into a small amount of limewater.
During a chemistry practical I have noticed that in some tests that I observe fizzing upon adding HCl.
Usually this means the presence of a carbonate ion.
However, the examiner's report often states that it is necessary to test the evolved gas with limewater.
How would I do this ? Usually I am carrying the test out in a small test tube and I am never provided with a gas syringe, connecting tubes or other apparatus.
So it is a logistics issue of getting the gas into a small amount of limewater.
Hate doing this... tilt the test tubes until they are almost horizontal and the mouths are touching, then seal the gaps with your thumb. Then wait for a few seconds. it's really just a matter of practcing and doing it again and again. And again. And again.
(edited 13 years ago)
Original post by UpsidedownLandMan
Hate doing this... tilt the test tubes until they are almost horizontal and the mouths are touching, then seal the gaps with your thumb. Then wait for a few seconds. it's really just a matter of practcing and doing it again and again. And again. And again.
So you mean one test tube will be filled with the limewater and the other with the solution being analysed ?
Yes. Should've said that.
Original post by Ari Ben Canaan
The most obvious is reacting a strong alkali with an ammonium salt.
Are there any others ?
What would happen if I heated SOLID CaO and NH4Cl ?
Are there any others ?
What would happen if I heated SOLID CaO and NH4Cl ?
Heating ammonim chloride , ammonium sulphates and ammonium carbonates all yield ammonia gas on heating
Original post by UpsidedownLandMan
Hate doing this... tilt the test tubes until they are almost horizontal and the mouths are touching, then seal the gaps with your thumb. Then wait for a few seconds. it's really just a matter of practcing and doing it again and again. And again. And again.
The things students have to put up with.
But, write that technique in your alternative to practical paper and guarantee yourself zero. Hypocrite exam boards!
Eh ?
What's an anti-terrorist hotline got to do with me or this thread ?
What's an anti-terrorist hotline got to do with me or this thread ?
Original post by jonathan3909
Heating ammonim chloride , ammonium sulphates and ammonium carbonates all yield ammonia gas on heating
So heating :
(NH4)2SO4 would give ammonia, water and SO2 ?
Original post by UpsidedownLandMan
Yes. Should've said that.
Are there any other tricky things or tips you have a chemistry practical exam ?
Original post by obviouslystudying
The things students have to put up with.
But, write that technique in your alternative to practical paper and guarantee yourself zero. Hypocrite exam boards!
But, write that technique in your alternative to practical paper and guarantee yourself zero. Hypocrite exam boards!
only if you don't have the proper equipment. I'd write it down using all the cool pipes and syringes etc, but in the lab (minus cool pipes etc), the two tubes technique works well enough.
Original post by Ari Ben Canaan
Are there any other tricky things or tips you have a chemistry practical exam ?
Erm... stick a sheet of (white) paper behind test tubes during identifications and behind the conical flask during titrations (i use the exam paper) but i think thats standard practice... learn the colours of compounds before the exam, so you can make a reasonable guess in the identification of compunds question (i.e. if it's blue, it's probably copper)... pretty much follow the questions word-for-word and go with as much detail as possible.
Original post by UpsidedownLandMan
Erm... stick a sheet of (white) paper behind test tubes during identifications and behind the conical flask during titrations (i use the exam paper) but i think thats standard practice... learn the colours of compounds before the exam, so you can make a reasonable guess in the identification of compunds question (i.e. if it's blue, it's probably copper)... pretty much follow the questions word-for-word and go with as much detail as possible.
Ah, thank you.
One other thing, when testing for ammonia gas we often add NaOH followed by slight warming.
How should I correctly carry out the test ? I dont want to get a false positive whereby the litmus papers turns blue because of the NaOH.
Original post by Ari Ben Canaan
Are there any other tricky things or tips you have a chemistry practical exam ?
Heating ammonium sulphate gives ammonia and sulphuric acid while heating ammonium carbonate gives ammonia , water and carbon dioxide.
Original post by jonathan3909
Heating ammonium sulphate gives ammonia and sulphuric acid while heating ammonium carbonate gives ammonia , water and carbon dioxide.
Wikipedia says Ammonia, Nitrogen, Water and SO2 are eveolved.
Original post by Ari Ben Canaan
Ah, thank you.
One other thing, when testing for ammonia gas we often add NaOH followed by slight warming.
How should I correctly carry out the test ? I dont want to get a false positive whereby the litmus papers turns blue because of the NaOH.
One other thing, when testing for ammonia gas we often add NaOH followed by slight warming.
How should I correctly carry out the test ? I dont want to get a false positive whereby the litmus papers turns blue because of the NaOH.
Try it without adding the NaOH if doubtful. Also, make sure the litmus paper doesn't make contact with the sides of the test tube, there could be NaOH residue there.
Original post by Ari Ben Canaan
Ah, thank you.
One other thing, when testing for ammonia gas we often add NaOH followed by slight warming.
How should I correctly carry out the test ? I dont want to get a false positive whereby the litmus papers turns blue because of the NaOH.
One other thing, when testing for ammonia gas we often add NaOH followed by slight warming.
How should I correctly carry out the test ? I dont want to get a false positive whereby the litmus papers turns blue because of the NaOH.
That's a test for ammonium salts and not ammonia.
Heat some of the unknown substance with sodium hydroxide solution.Note the smell of any gas evolved and test it with a moist red litmus paper.It turns blue.
Original post by Ari Ben Canaan
Wikipedia says Ammonia, Nitrogen, Water and SO2 are eveolved.
Thats only on really strong heating.You don't need to know all these-
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