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Author: Subject: Sodium bisulfate questions & reactions
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[*] posted on 26-6-2021 at 01:29
Sodium bisulfate questions & reactions

I got a kilo of sodium hydrogen sulfate as ph lower chemical for pool. I think that i could use it as a relatively safe and easy to get alternative to sulfuric acid. Now i got some doubts about it, so here are some questions:

By adding boiling water to a mix of NaHSO4 and NaCl, is any hydrogen chloride formed? Does the temp have to be that high or small amount may form at 100 C?

Is sodium bisulfate able to make acids from salts in solution? For example i noticed that hydrogen sulfate alone in solution isn't able to corrode visibly aluminum, but if there is an equal amount of sodium chloride it is eaten very very quickly, as hydrochloric acid would do.

In the route to sulfuric acid via NaHSO4, this salt is heated to around 600-700 C first to form sodium pyrosulfate and then to crack it into sulfur trioxide. But if the pyrosulfate hydrolizes in water to sulfuric acid, why does it need to be cracked at that high temperature if it could be just dissolved in water to get some sulfuric acid?

How can i make sulfate salts from it? It doesn't look to dissolve much metals, except magnesium. I left overnight a concentrated solution of NaHSO4 and hydrogen peroxide with copper in it, hoping that in the morning i could have got some copper sulfate. It didn't look blue at all, nor any copper looked to be corroded.

What experiments can i do with it? (Already done a few things found on the golden chemistry book, such as HCl from salt and ethyl acetate with vinegar and alcohol)


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[*] posted on 26-6-2021 at 02:13

NaHSO4 is like any typical acidic compound. You can get a about ph 1 or so I think. Like any ionic compound, it lives in equilibrium with all the other ions. You'll have a mixture of ions like Na+, HSO4-, H+ (H3O+), SO4--. If you add NaCl to it, you have more Na+ as well as Cl- in the mixture.

When there is a source for H+ and Cl-, HCl(g) is liberated depending on conditions. If the consentration is high and/or mixture is warmed (heat reduces HCl solubility in water and increases vapor pressure of HCl). More HCl gases at elevated temperature, less at cooled temperature. You can check it out easily by pH paper or use water to absorb liberated HCl. You can eg. take a container and put in a beaker with the mix with a beaker of water and you'd (slowly) get some (dilute) hydrochloric acid when it vaporizes from the mix and dissolves in water.

If you want to dissolve metals you need something that oxidizes the metal. Aluminium dissolves in HCl because after oxide layer is removed it reacts with water. I've no idea why your test with hydrogen peroxide didn't dissolve copper. Acidic H2O2 should react quite well with copper. Such mixtures are used to etch PCBs and they work very well based on my experience. Acidic H2O2 should for quite a few other metals too.

If you're making metal sulfates, you'll have the problem with other ions. After some metal has dissolved in the liquid, you still have the Na+ ions there (and chloride if you added NaCl). Unless the metal sulphate has low solubility in the mixture, things can get difficult to purify. Of course, you can manipulate solubility by keeping sulfate concentration as high as possible. Typically sodium compounds tend to be quite soluble and often will not participate out too easily.
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[*] posted on 26-6-2021 at 07:22

Making sulfate salts from NaHSO4 isn't good idea. It will be hard to separate your metal sulfate from sodium sulfate. Some divalent metals form double sulfates with composition A2M(SO4)2.6H2O (A = K, NH4, Rb, Cs, Tl), (M = V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd). So if you can get KHSO4, you can make these sulfates pure.

You can use NaHSO4 to make H2SO4 by membrane electrolysis (you can use flowerpot as membrane).

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