Acid Mixture - HF+HCl+H2SO4

[lanrete]

Hi,

 

i have a mixed acid sample of HF+HCl+H2SO4 and i need to find out the individual concentrations of the 3 acids. How can i do so?

 

Urgent help needed. Thanks.

[Wookiee]

Its really not that hard aslong as you know what molarity and volume of each acid before you mixed them.

 

You deffinetly need more information for this to be answered.

 

-Randy

[lanrete]

Thats the problem. The molarity and concentration is unknown to me and i need to find it out analytically.

[Wookiee]

I am also assuming you want to keep the majority of the solution, if not all of it?

Well either way. I wouldn't know how to do it. Sorry, others here with more experience might be able to.

 

-Randy

[lanrete]

Thanks for trying. I hope some chemistry experts can help me out here.

[YT2095]

Barium chloride titration will establish the H2SO4 content the 2 halic acids are little tougher as silver nitrate would likely react with both at the same time, so you would probably have to distill them, and when you notice a sharp jump in temp on the thermometer, measure how much has come over already.

 

on second thoughts forget that, Hot HF will kill your glassware!

 

this is indeed a good question

[lanrete]

Thanks for your input YT2095. I have found that H2SO4 can be isolated by evaporating the sample over a waterbath. This removes both HF and HCl leaving H2SO4 of which the content i can determine with a simple titration with NaOH.

 

Now the problem is how to seperate HF or HCl from the mixture so that i can do another titration to determine the halide acid concentration.

[John Cuthber]

You might want to dilute the solution first.

IIRC silver fluoride is soluble so titration with AgNO3 might work for HCl. Not sure if sulphate would interfere. You could try to ppt it with Ba(NO3)2 first but I think BaF2 is insoluble so that migt be tricky.

 

The best way if you have access to the right equipment is to neutralise the stuff and measure the ions chromatographically. That way you don't need to drive off the HF as the vapour (and that's not a nice experiment btw).

I think there's probably a way to do this by precipitations and or titrations on the stuff without making the nasty fumes.

A titration against standard alkali will get the total acidity (and the H2SO4 concn if you are careful and lucky, the bisulphate ion should be distinguishable from the other acids if you use a pH meter while you titrate.)

 

I think that MgF2 could be precipitated by adding MgNO3 and this could be filtered washed dried and weighed to give the HF concn.

Then you could add Ba(NO3)2 to ppt BaSO4 to measure the H2SO4. Finally you could measure HCl by difference or by titrating with AgNO3.

Good luck, and be careful with the HF.