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Topic: How to distinguish between NaHSO4 and Na2SO4 in lab using these reactants?  (Read 1177 times)

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Offline chenbeier

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Re: How to distinguish between NaHSO4 and Na2SO4 in lab using these reactants?
« Reply #15 on: September 27, 2020, 02:12:53 PM »
Hydogensulfat is also a sulfate, it dissociates. Why would it react with Barium ions, the precipitate is Bariumsulfate not Bariumhydrogensulfate.

Even Sulfuric acid is a sulfate. Dihydrogensulfate.

The exercise was to use the given chemicals in the table to figure out, which chemical is in the two samples. No indicator to use.

Offline AWK

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Re: How to distinguish between NaHSO4 and Na2SO4 in lab using these reactants?
« Reply #16 on: September 27, 2020, 02:52:29 PM »
Barium hydrogen sulfate can be obtained from barium sulfate in concentrated sulfuric acid. When diluted with water, barium sulphate will precipitate.
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Offline chenbeier

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Re: How to distinguish between NaHSO4 and Na2SO4 in lab using these reactants?
« Reply #17 on: September 27, 2020, 02:59:32 PM »
That is possible of course. But here we have two aquaeous samples.
I answered because we don't have two sulfate was told and this I disagree.

Offline Borek

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Re: How to distinguish between NaHSO4 and Na2SO4 in lab using these reactants?
« Reply #18 on: September 27, 2020, 06:35:49 PM »
One solution is highly acidic, the other is neutral, that's what is important here. You can be nitpicky about whether these are both sulfates, but your question about why to compare dissociation constants suggested you are overlooking the most important property by which these solutions differ.
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Offline chenbeier

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Re: How to distinguish between NaHSO4 and Na2SO4 in lab using these reactants?
« Reply #19 on: September 28, 2020, 01:20:14 AM »
Everything ok, what you are saying, nur it doesnt help if I have the two samples in the hand.
If I know the two K values, what to do next.

Offline Borek

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Re: How to distinguish between NaHSO4 and Na2SO4 in lab using these reactants?
« Reply #20 on: September 28, 2020, 03:17:34 AM »
The stronger acid replaces the weaker acid, HCO3- gets protonated and decomposes, this is exactly a HS level reasoning necessary here. TBH, knowing your level of expertise I am not sure if you are not trolling now.
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Offline chenbeier

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Re: How to distinguish between NaHSO4 and Na2SO4 in lab using these reactants?
« Reply #21 on: September 28, 2020, 06:35:42 AM »
I am not trolling. We have two tubes with one of  sodium sulfate and one of sodium hydrogen sulfate.
A list of some chemicals are given to find out what is what.
The TES picked Bariumchloride, what is ok to determine sulfate. Also he want to take NaOH, but this is without indicator or pH probe not possible, to get a result.
At the end I gave a hint for the baking soda, which would react with the hydrogen sulfate.
The miracle is solved.

Between AWK came up with the discussion of k values of carbonic acid and sulfuric acid. But this will not help, if the TES don't know what is going on. It would be same we you  know the a melting point of both but they are dissolved., if not can heat up. Probably it is a paperwork and no lab exercise.

Carbonate came into the rule after baking soda was picked up.
My answer was still, what to do with a k value if carbonate is not in the game.

Offline AWK

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Re: How to distinguish between NaHSO4 and Na2SO4 in lab using these reactants?
« Reply #22 on: September 28, 2020, 08:31:08 AM »
My hint regarding the acidity constants of carbonic and sulfuric acid (K2) is the theoretical basis for selecting NaHCO3 for the NaHSO4 test.
Students learn about acid strength (acidity constants) and how they apply to predict the direction of chemical reactions at the very beginning of general chemistry. You probably missed something in your study - carbonic acid contains two active protons.
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Offline chenbeier

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Re: How to distinguish between NaHSO4 and Na2SO4 in lab using these reactants?
« Reply #23 on: September 28, 2020, 10:49:18 AM »
You are right, but before to do so has to have the expierence to pick the right one.
Some people pick maybe Permanganate or copper sulfate, what of course makes no sense.
So given two samples and the list of chemicals. Do you check all physical parameters of each to find out what is for? In my case no. The expierence and the practise is to know that sodiumhydrogencarbonate release gas CO2. Prepared my self candy with strawberry an citric acid and baking soda and not looking up some k values.

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