Will a solution of H_2SO_4//SO_4^(2-) be a buffer? Why or why not?

1 Answer
Truong-Son N.
Jan 26, 2018

No. In fact, the sulfuric acid would greatly protonate "SO"_4^(2-), probably completely, and then you would just get one bisulfate species for the most part. That is not a buffer.

A buffer is best made between some weak electrolyte and its conjugate.

Thus,

  • If you were to use "SO"_4^(2-), then it must be paired with "HSO"_4^(-).
  • If you use "NH"_3, you must pair it with "NH"_4^(+).
  • If you use "CH"_3"COOH", you must pair it with "CH"_3"COO"^(-).

"H"_2"SO"_4 is a strong acid... so it cannot be paired with anything to make any decent buffer.

CHALLENGE: What should the maximum ([SO_4^(2-)])/([HSO_4^(-)]) ratio be in order to make the best buffer?

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