Water tests and ion tests.. do we need to knwow (1 Viewer)

[ribeena]

for the water tests and ion tests do we need to descibe them or do we need to just identify them???
like do we need to state chemicals and stufff
hope u can help me..

 

[tennille]

I would learn the chemicals and all that because you were meant to carry out a first hand investigation using the water tests (which we never did). If you have Conquering Chemistry, that epxlains a variety of tests.

 

[tennille]

I think the verb used is identify, but that is kind of naming and descrbing as well.

 

[ribeena]

but theres heeps...theres like 6 water etsts and like heeps of metal ions.....

 

[tennille]

I know, that's what's killing me for studying

They'd probably ask you to describe one water test (they'd probably specify as well otherwise poeple will just state hte turbidity one which is pretty simple). The worst ones are DO and hardness.

 

[tennille]

it states "identify that water quality can be determined by considering...". You have to have some knowledge of it, especially when there's a prac that you have to do to determine water quality.

 

[mazza_728]

How do u remember the anion and cation precipitate tests? I cant!!
Does anyone know if barium phosphate is soluable or not?

 

[tennille]

Barium phosphate is insoluble.

 

[Paroissien]

I don't know. Just write them down over and over again. I don't think there are any special tricks, but knowing the solubility rules helps

 

[tina_goes_doo]

Yeah i'm making a big deal of trying to remember them all. I can remember the general rules but then there's alway exceptions like lead! I'm thinking alright, lead forms ppts with a lot of things, but then it can form slightly soluble ppts as well which dissolve in hot water. Basically i'm trying to visually picture what the table looks like.

 

[Paroissien]

Just remember lead is slightly soluble in chloride with cold water, and totally soluble with chloride in hot water.
There is a white ppt formed which could be either silver or lead. Heat the solution, and if dissolves, it is lead

 

[mazza_728]

I just got off the fone to the advice line -- the chick was no help! so i thought maybe u guys would know. since barium phosphate is supposedly insoluable wouldnt it affect our lawn fertiliser results? remember the prac where we found the sulfate content in lawn fertiliser - we crushed fertiliser, added acid, added excess ba ions (BaCl), filtered and dried/weighed. doesnt fertiliser contain phosphate ions as well? and so when we add "excess Ba ions" wouldnt the phosphate precipitate out too and so effect our results?

 

[Xayma]

Yep, that is one of the things you should talk about if it asks for the validity of the responses.

 

[mazza_728]

well yeah thats wat i thought i could do but it doesnt make sense because our results for the sulfate experiment were pretty accurate most people in my class was 1-2% off.. which isnt much! so im really confused!

 

[Xayma]

Well the phosphate will over give the result but then the filtering of the fine grains of which some will escape will bring it down, plus undissolved material will get caught

 

[Not Too Bright]

i thought our class used NH4S04 fertisiler so there would be no phosphate

phosphate can be detected by ammonia molybdate it produces yellow precipitate forms every 5 minutes free thats the facts i remember

 

[AR]

since barium phosphate is supposedly insoluable wouldnt it affect our lawn fertiliser results? remember the prac where we found the sulfate content in lawn fertiliser - we crushed fertiliser, added acid, added excess ba ions (BaCl), filtered and dried/weighed. doesnt fertiliser contain phosphate ions as well? and so when we add "excess Ba ions" wouldnt the phosphate precipitate out too and so effect our results?

the reason that you add acid after you crush the fertiliser, is to make it acidic conditions - barium phosphate only forms under conditions that are slightly alkaline, which means that all the barium will react with the sulfate ions. but this prac was on the hsc last year i'm think, so chances are it wont be there again.