strong-acid strong-base question

[243_robbo]

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when H2SO4 reacts with NaOH it produces NaHSO4 and H2O

because both the acid and the base are strong, the pH should be neutral and the Na+ and HSO4- ions should not react to any sginificant as they are extremely weak conjugates.

However our prac yielded a pH of 3 and the teacher concurs that the HSO4 should act as an acid and react with water to produce H3O+ and SO4 2-.

HSO4 is amphiprotic and so it can act as an acid or a base, but why in this case is it acting as a stronger (but still weak) acid again rather then being a weak base as conjugates should. And why is a strong acid-strong base salt yielding such a low ph

this is very confusing so i hope i explained it properly

thanks in advance if anyone can help

[Dreamerish*~]

Sounds to me like H₂SO₄ was in excess.

By the way, it reacts with NaOH to produce Na₂SO₄. I think there should be some hydrogen sulfate too, but this is what my teacher told me after I got it wrong in an exam.

[insert-username]

I'm pretty sure H₂SO₄ reacts with NaOH to give Na₂SO₄ (sodium sulfate) and water at a ratio of one mole of sulfuric acid to two moles sodium hydroxide. I don't think they react to give a hydrogen sulfate.

I would guess that in your prac you had insufficient NaOH to react with the H₂SO₄. Hence, the available NaOH reacts with the acid to form Na₂SO₄, and the remaining acid is left bumming around. The presence of the acid results in the very low pH of 3.

EDIT: Damn, Dreamerish wins by a nose.


I_F

[243_robbo]

cool thanks that helps a bit