water stuff (1 Viewer)

[Toodulu]

eh how does calorimetry and hard/soft water come into anything aaaand do we need to know 14.1 in chem context? (the algal blooms, cave formation etc)

 

[P.I.M.P.]

hard water has Mg and Ca ions in it. u can use the lathering of soap to test for them=> more ions, less lathering

 

[hipsta_jess]

yep, you can use either the lather test (you want it to be soft-ie, lots of lathering) or an AAS if you really wanted too.

 

[Constip8edSkunk]

another quantitative test is by titration against EDTA which binds the Mg and Ca ions, using an eriochrome black-T indicator that turns from red to blue with purple as the end pt

edit: dun need 2 know cave formations, need 2 talk about algal blooms in terms of eutrophication

 

[toknblackguy]

i dunno what calirometry is, but the preferred test for hardness is titratino of the water sample with EDTA. all i remember is that the stoichometric ratio fo Ca2+ : EDTA is 1:1

 

[ND]

IIRC you can use colorimetry to determine the phosphorus in water (convert it to phosphate first). Though the easy method is obviously gravimetric analysis.

 

[inasero]

using an eriochrome black-T indicator that turns from red to blue with purple as the end pt

wrong bro...its the other way around

 

[toknblackguy]

wait a sec...so is EDTA erichromeblack-T?

 

[ND]

No i think EDTA is a solution with complexs, and eriochrome is the indicator.

 

[inasero]

actually john forgot to mention that you should add a NH3/NH4+ buffer solution first b4 titrating

 

[toknblackguy]

oh
so when testing for hardness
you titrate the sample against edta, using erichromeblack-t as the indicator
hopefully i remember that

 

[Constip8edSkunk]

Originally posted by inasero
wrong bro...its the other way around

same thing wilson, it depends on what u put in the burette and what in the beaker.... lol

Originally posted by toknblackguy
wait a sec...so is EDTA erichromeblack-T?

no one is the titrate, the other is the indicator

 

[ND]

Isn't that just for Mg though? Shouldn't you precipitate out the Ca first? (as you can tell i haven't actually done this)

edit: or find some way to mask one of them.

 

[Constip8edSkunk]

i thought it binds to both Mg and Ca, holdon...lemme check...

edit: Yeah according to Macmillan pathways, it measures both, though it didnt account for Mg in its caluclations....wierd (see Page 279-80)

 

[loser]

I thought for hardness, you precpitate the Mg and Ca ions, and use gravimetric analysis.

 

[ND]

Originally posted by Constip8edSkunk
i thought it binds to both Mg and Ca, holdon...lemme check...

edit: Yeah according to Macmillan pathways, it measures both, though it didnt account for Mg in its caluclations....wierd (see Page 279-80)

Yeh that's why i said you'd have to mask or remove one, cos you won't know how much is Ca and how much Mg.

 

[Constip8edSkunk]

true dat.

 

[loser]

I thought for hardness, you precpitate the Mg and Ca ions, and use gravimetric analysis.

?

 

[ND]

Originally posted by loser
I thought for hardness, you precpitate the Mg and Ca ions, and use gravimetric analysis.

?

Yeh you could do that (i think the Mg precipitates out as something with ammonia and phosphate in it, i don't remember...).

 

[Constip8edSkunk]

could do it both ways...

even AAS can be used as well.... i think