July 14, 2024, 08:24:34 PM
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Topic: How do I calculate the pH of a 0.1 M solution of (N2H5) (HSO4)?  (Read 430 times)

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Offline dolphinsea14

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Hydrazine (N2H4) is a weak diprotic base (Kb1 = 8.5∙10–7; Kb2 = 8.9∙10–16). It can form

various anhydrous salts with sulfuric acid. The second acid dissociation constant of

sulfuric acid is Ka2 = 1.02∙10–2.
pH should be 1.57. I obtained this correct value, but I didn’t get the same cubic equation. In my equation the first member in the second bracket 𝐾𝑏2/𝐾𝑤 is missing. I took into consideration the hydrolysis of N2H5+, dissociation of HSO4- and autoprotolysis of water, but I am missing something.

Offline Borek

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Re: How do I calculate the pH of a 0.1 M solution of (N2H5) (HSO4)?
« Reply #1 on: June 23, 2024, 02:34:39 AM »
Hard to comment not seeing the derivation.

Technically there 5 equilibria present - two for the acid, two for the base, one for water, so there are 5 equations that needs to be combined, and the final equation should be not cubic, but of 5th degree. In this case of these equilibria one for the acid and one for the base can be safely neglected if all you are interested in is a practical result, not a theoretical formula.
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