Science Experts? Chemistry Q
- Thread starter Butters
- Start date
- Status
Useful.
(Along with another useful post from me too. Considering I did that in chemistry and don't remember at all it's even more useless.)
Other half has a question about planning an experiement for determining the concentration of NaOH.
She has to plan two methods one of which is titration, the other she has to work out.
Any pointers, she'd be very grateful.
Titration is the only thing I can think of to work out the concentration....
I suppose reacting the NaOH with an excess of HCl then filtering off the salt and wieghing it, working out how man moles of NaOH were orginally there by taking into account the volume of NaOH reacted and the moles of NaCl produced.
HCl, hydrochloric acid.
Associate
- Joined
- 8 Nov 2006
- Posts
- 420
- Location
- Loughborough
Not that helpful really. If you have to do this in a lab....
Associate
- Joined
- 8 Nov 2006
- Posts
- 420
- Location
- Loughborough
Yeah using those equations i can't remember. (ph is a measurement of H+ ions present?!)
How accurate does it have to be? If you want a ball-park figure (or a thought experiment) there are lots of ways surely: density, pH, viscosity. Does NaOH absorb UV?
M
on the same note as the HCl route you could precipitate an insoluble salt of sodium (since NaCl is water soluble).
hmmm, let me think......i don't think that will work as there are so few insoluble sodium salts, may have to scratch that idea.
ermm, measuring the pH is the obvious answer - i assume you want a chemical method??
how about, you add some iron (III) chloride - i think the insoluble iron hydroxide should form which you can filter, dry and weigh and work out the no. of moles of hydroxide that way.
hmmm, let me think......i don't think that will work as there are so few insoluble sodium salts, may have to scratch that idea.
ermm, measuring the pH is the obvious answer - i assume you want a chemical method??
how about, you add some iron (III) chloride - i think the insoluble iron hydroxide should form which you can filter, dry and weigh and work out the no. of moles of hydroxide that way.
OK, thanks for the methods. Re the HCI route, she is asking:
if I used 25cm cubed of NaOH, what would be a sensible amount of HCl to use...should I add a pH indicator and stop adding the acid when the colour turns green (neutral)? And should I just filter the result or heat it and let the salt crystalise?
if I used 25cm cubed of NaOH, what would be a sensible amount of HCl to use...should I add a pH indicator and stop adding the acid when the colour turns green (neutral)? And should I just filter the result or heat it and let the salt crystalise?
won't work - NaCl is too water soluble (about 33g per 100ml water if i remember correctly). Apart from measuring the pH i think the best way is to precipitate an insoluble compound and filter off. There are no suitable sodium salts so you need an insoluble hydroxide - i think the iron example i said above should work - i'm very rusty on the simple stuff though
- Status