I'm modelling the concentrations in the Belousov Zhabotinsky reaction. For this model, I need to convert [BrO3-] to [HBrO3]. I discovered in several papers that the following correlation applies:

$$ [\ce{HBrO3}] = \frac{h0}{h_0+0.2} * [\ce{BrO3^-}]_0 $$

See for example this dissertation on page 28 or this paper on page 2.

I have a solution which has $[\ce{H2SO4}]$ = 0.915M (I assume $[\ce{H+}]$ = 1,830 M).

My $[\ce{BrO3^-}]$ was 0,2411 M.

I researched the Hammett Acidity function, but I still don't completely understand the concept. What I do know is that $h_0$ substitutes for $[H+]$ and that $h_0$ has the unit of M.

Can anyone explain the concept of this function in a bit more detail and explain in what way it exactly relates to pH (and therefore to H+)?

On the internet I found this paper, which says that $h_0$ = 3 when $[\ce{H2SO4}]$ = 1.5M. Are there any other tables or references with $h_0$ related to the concentration of $\ce{H+}$ or $\ce{H2SO4}$? There is one more question on SE about Hammett acidity. This question links to tables with $h_0$ for certain % of H2SO4. Can I perhaps use that? How does $[\ce{H2SO4}]$ relate to a % of H2SO4?

Is there a way to calculate the $h_0$ when $[\ce{H2SO4}]=1.830 M$?

  • $\begingroup$ Just plug pH-meter in there and used the values you get - H0 is approx. = pH for diluted sol. $\endgroup$ – Mithoron Nov 7 '20 at 20:15
  • $\begingroup$ Oke, thanks @Mithoron! So in this case, I assume H3O+ = 1.830 M, my pH = -log(1.830) = -0.262 and I can assume h0 = -0.262? Because when h0 = -.262, the [HBrO3] would be 1,01 and that's about four times the amount of BrO3- I added... But well, you're perhaps the wrong person to ask this, whilst you didn't devise the formula😉 Thanks anyway! $\endgroup$ – ralphjsmit Nov 9 '20 at 11:48
  • $\begingroup$ As Karsten mentioned, you assume wrong, more so H2SO4 is not the only thing affecting pH in such mixture. $\endgroup$ – Mithoron Nov 9 '20 at 15:34
  • $\begingroup$ Hi Mithoron, thanks for pointing that out again. The formule here is about the initial concentrations, so you kind of cancel out the other things affecting pH in such a mixture. I'm just secondary school and there we assume that H2SO4 completely becomes H+. As this thing isn't at a very advanced level, I'll for now just assume H0=[H+]. $\endgroup$ – ralphjsmit Nov 9 '20 at 15:40

I have a solution which has $[\ce{H2SO4}]$ = 0.915M (I assume $[\ce{H+}]$ = 1,830 M).

While $\ce{H2SO4}$ is a strong acid, $\ce{HSO4-}$ is not ($\mathrm{p}K_\mathrm{a}$ around 2). So your pH should be about zero, and you might not need to use the Hammett acidity at all.

  • $\begingroup$ Hi Karsten, thanks for thinking along. The thing is that I need to calculate the HBrO3 concentration. One of the ways I could do this is by using the aforementioned formula. Because of that I do need to use the Hammett Acidity function. Would that mean that my Hammet acidity function is roughly zero? And is there a way of calculating that? $\endgroup$ – ralphjsmit Nov 7 '20 at 14:49

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