modelling a solvay step (1 Viewer)

[mr EaZy]

Hi guys!

im not sure on this one coz most model answers describe the decomposition of NaHCO3.

i wanna do brine purification:

1)fill a 500ml beaker with 300ml salt water
2) Add 3 drops phenolphtalein
3) slowly titrate 2M NaOH solution and watch the mgOH and CaOH ppt out of solution and wait for the purple colour.

$) when the purple colour comes out, this would mean that no more ppt will form and that the brine is purified!

is this okj????

 

[mojako]

well solvay process has several components
u shud know all if u can
probably just know the main eqns and make up the steps on the spot ^^

brine purification isnt one of the major ones to model,
so I'd think that its a little inappropriate...
u can assume its pure enough actually..
model the other parts..

 

[beta-omega]

I agree with mojako about using a different method, but on Brine Purification,

Ca(OH)2 is actually partially soluble, so this is not a good method, but its effective for magnesium.. Plus there would be the presence of other anions that you can not get rid of such as sulfates.

Evaporation of the solution, because as the concentrated solution evaporates, impurities such as calcium sulfate crystallise out first as a scale on the side of the salt pond. The sodium chloride itself crystallises next, and leaves most of the other more soluble contaminants behind in the solution. Then you extract the NaCl and redissolve it in to some water.

You can also sature the solution with HCl, remebering that all ionisation reactions are in fact equilibriums, saturating the solution would then push the equilibrium back towards crystalising out the NaCl.

You can add sodium carbonate to precipiate out the calcium.

 

[mr EaZy]

k thnx
im doin the carbonating step now

 

[SelphieBoffin]

I disagree. I think brine purification in one of the major steps of the Solvay process.
In the syllabus it says
'describe the chemistry involved in:
- brine purification
- hydrogen carbonate formation
- formation of sodium carbonate
- ammonia recovery'
so it would seems as though brine purification is one of the four major steps according to the syllabus, no?

 

[beta-omega]

sure it is a necessary step, yet there isn't much you can do with it, and also note that the syllabus states that you need to talk about problems associated with it... the formation of NaHCO3 is quite relevant as you can not decompose CaCO3 under standard conditions using a bunsen.

 

[mr EaZy]

oh, tru that mate, ill take that into my modelling step

 

[SelphieBoffin]

True, you do need to talk about the problems involved. Good point.

 

[mojako]

.....

True, you do need to talk about the problems involved. Good point.

interesting quote..
EDIT: oh, sorry. I was trying to figure out how you made that line and I pressed Quote and I somehow thought the line was because you wrote [Quote=yourself...