## vera_ewing one year ago For the weak hypochlorous acid (HClO), which statement is true at the point halfway to the equivalence point? A. The total amount of HClO is equal to the pKa. B. The total amount of HClO is equal to ClO-. C. The total amount of H3O+ is equal to the amount of OH- . D. The total amount of ClO- is equal to the Ka of the acid.

1. JFraser

the half-equivalence point is a very important point of a titration. If you are titrating exactly 1.00mol of a weak acid with a base like NaOH, once you've added 0.500mol of the $$OH^{-1}$$ ion, you've used exactly $$half$$ of the acid, right?

2. vera_ewing

Right, okay.

3. JFraser

When the general reaction is$HA + OH^{-1}(aq) \rightarrow A^{-1}(aq) + H_2O$and if you use an ICE table approach, you get:

4. JFraser

if you start with 1.00mol of HA, and react half of it, you're left with 0.500mol of acid HA left over, but you've also $$formed$$ 0.500mol of the conjugate, $$A^{-1}$$

5. Rushwr

Hey there I'm not sre with my answer though I'll be telling you my opinion on this ; I will go with the answer 2 or 3

6. JFraser

it's not C. are you familiar with ICE tables for equilibrium problems?

7. Rushwr

C or B I"m not sre with that

8. vera_ewing

It's B?

9. Photon336

H3O+ and OH- would be the equivalence point pH = pKA + LOG[1] so it's not C

10. JFraser

at the half-equivalence point, you've used up half of the $$HA$$, but formed half of the $$A^{-1}$$

11. Rushwr

then is it B is what I am asking @Photon336

12. Photon336

Don't know why I find this confusing if you use up half of the HA and form half of A- then pH = pKA Then at this point the pH = pKA at half equivalence point. Think I mixed it up.

13. Photon336

If that's true then the amount of HClO = ClO- B