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### Topic: how to determine the concentration NaOH without titration?  (Read 17309 times)

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#### ARGOS++

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##### Re: how to determine the concentration NaOH without titration?
« Reply #15 on: April 16, 2008, 07:58:00 PM »
Dear Williec;

If you feel confident that all Na+ is only from NaOH, you can use:  "Uranyl Zinc Acetate”.

Good Luck!
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#### A2 student

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##### Re: how to determine the concentration NaOH without titration?
« Reply #16 on: April 21, 2008, 04:29:38 PM »
Hi,
I'm doing this paper too; basically ... just to clear up as some posts seem to be a little irrelevant to what we are trying to figure out! ... we've been given the NaOH solution with an "approximate concentration of 2mol dm-3". We have to find the conc "as accurately as possible" BOTH methods have to include chemical reactions (ie so cant use a pH meter) and only one is allowed to use a titration.

To me this is as close to my thinking as I've seen:

Gravimetric analysis.
and
If you feel confident that all Na+ is only from NaOH, you can use:  "Uranyl Zinc Acetate”.
but the thing is the whole uranyl zinc acetate thing is a bit far fetched I think ... they want us to use substances that we use in a college lab.

Does anyone know of anything else that's insoluble in NaOH because I don't really know how you figure that out! (it does have to be insoluble doesn't it in order to form a precipitate and then weigh it?)

Also ... once you have the precipitate ... what exactly would it be and how do you calculate the conc of NaOH from it?

Am fine with calculating it from a titration but this bit loses me!

Thanks muchly for any help given!
x

ps. sorry for the loooong post!

#### Borek

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##### Re: how to determine the concentration NaOH without titration?
« Reply #17 on: April 21, 2008, 04:49:50 PM »
If you feel confident that all Na+ is only from NaOH, you can use:  "Uranyl Zinc Acetate”.
but the thing is the whole uranyl zinc acetate thing is a bit far fetched I think ... they want us to use substances that we use in a college lab.

So perhaps you should try to assume that all OH- is only from NaOH and look for hydroxide that can be precipitated and filtered out?
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#### A2 student

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##### Re: how to determine the concentration NaOH without titration?
« Reply #18 on: April 21, 2008, 04:54:35 PM »
So perhaps you should try to assume that all OH- is only from NaOH and look for hydroxide that can be precipitated and filtered out?

okay, so would
NaOH + FeCl3 work forming a precipitate of Fe(OH)3 ... or am I making that up???

#### Borek

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##### Re: how to determine the concentration NaOH without titration?
« Reply #19 on: April 21, 2008, 05:14:13 PM »
Nice try

Now try to use Google for a general idea about how to do it...

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#### m00

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##### Re: how to determine the concentration NaOH without titration?
« Reply #20 on: April 21, 2008, 06:54:24 PM »
Ok i have this paper too and yes alot of the answers so far have been helpful for a degree standard however, the best solution for a second experiment supposably is an enthalpy change. You use hydrochloric acid and measure ethalpy of neutralisation or something, can anyone tell me how you can use this to work out concentrations of NaOH. I know you can do an enthalpy experiment neutralise the NaOH with a certain amount of HCL, but how can u do the calculations?. Any detailed answer about what you would do be grateful ty.

#### mnakhla

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##### Re: how to determine the concentration NaOH without titration?
« Reply #21 on: May 06, 2008, 01:15:44 AM »
enthlapy change? do they want you to do it calometrically maybe and use molar bond energies of formation  of NaCl and water to calculate how much naoh...but hcl also releases heat when placed in water so you would have to look up the amount of heat released and precisesly measure out the amount of water and then subtract the amount of heat that would be evolved ...but you would have errors due to the fact that the naoh changed the volume of the water...

after that you'd have to compare the heat of formation of naoh and nacl/water to compare how much energy went where and by calculating the total diffrence in temprature and coverting it to joules you should be able to calculate the amount of naoh present...sorry if this wasnt clear im having a hard time explaining what was going through my head
and
sorry this was just a stab in the dark..
Im a freak and Im quite fond of it