# CHEMISTRY

posted by .

A question asks to find out the pH at the half-neutrilization point. Can someone please explain what this is?

I think it should be that half the moles of the base NH3(being titrated with a strong acid, HI) have been neutrilized, but if this is so, I'm still stuck on how to approach the problem.

We only know the concentration+ volume of NH3 and the conc. of HI.

• CHEMISTRY -

For a weak acid, HA, being titrated with a strong base, such as NaOH, we have the equation,
HA + NaOH ==> NaA + H2O.

Now what is the Ka for the acid?
HA ==> H^+ + A^-
Ka = (H^+)(A^-)/(HA)
Let's solve for (H^+). That is
(H^+)=Ka*[(HA)/(A^-)]
Now let's turn our attention to the equation. Suppose we start with 2 moles HA. So when we get half way to the equivalence ponit (the equivalence point is when we have added 2 moles NaOH), we will have 1 mole HA left. Right? And how much NaA will have formed. Of course that's 1 mole has been formed because that's how much HA has been titrated. Now look at the equation. Plug in 1 for HA (that's whats left) and 1 for A^- (that's how much of the salt that's formed) and (H^+) = Ka. Neat, huh? It always works that way. When you are half-way to the equivalence point of a weak acid, (H^+) = Ka. When you are half-way to the equivalence point of a weak base, (OH^-) = Kb.

## Similar Questions

1. ### Chem+ASAP+2 fill in the blank questions+ASAP!!!

PLease check this. They are fill in the blank and I just need to know if they are right. Thanks! 9. Compared to a strong acid-strong base titration curve, a weak acid-strong base titration curve has a (higher, lower) __higher___ initial …
2. ### titrations

I have to find the correct acid-base indicator to use for the following titrations (methyl orange with end point @ pH 4, bromthymol blue with end point @ pH 7, or phenopthanlein with end point @ pH 9). I have several problems given …
3. ### Chemistry (A level)

I was given a Chemistry question on the titration of a strong base being added to a weak acid. The question was: "Calculate the pH in a titration when 10.0cm^3 of a 0.10moldm^-3 solution of NaOH is added to a 10.0cm^3 of 0.25moldm^-3 …

When a monoprotic weak acid is titrated with a strong base, the titration curve contains these many inflection points: a.zero b.one c.two d.three Can you also explain why you choose your answer to this question...thanks
5. ### chemistry

if 0.4M NaOH is titrated with 0.4M HF, how do we calcualte the ph at equivalence. The book assumes each is 1L, but why do we use 1L * chemistry - Dr.Jim, Thursday, November 11, 2010 at 5:31am HF is a weak acid, so you need the dissociation …
6. ### Chemistry

HOBr (aq) <----> H+ (aq) + OBr- (aq), Ka = 2.3 x 10^-9 Hypobromous acid, HOBr, is a weak acid that dissociates in water, as represented by the equation. (a) Calculate the value of [H+] in a solution of HOBr that has a pH of 4.95. …
7. ### Chemistry

I'm trying do this question: 0.10 mol/L hydrochloric acid is titrated with 0.10 mol/L methylamine, CH3NH2. Calculate the pH of the equivalence point. I'm having trouble with the equation... How do you know what HCl + CH3NH2 will produce?
8. ### Chemistry

The half-equivalence point of a titration occurs half way to the end point, where half of the analyte has reacted to form its conjugate, and the other half still remains unreacted. If 0.220 moles of a monoprotic weak acid (Ka = 5.7 …
9. ### chemistry

The half-equivalence point of a titration occurs half way to the end point, where half of the analyte has reacted to form its conjugate, and the other half still remains unreacted. If 0.460 moles of a monoprotic weak acid (Ka = 3.8 …
10. ### chemistry

The half-equivalence point of a titration occurs half way to the end point, where half of the analyte has reacted to form its conjugate, and the other half still remains unreacted. If 0.220 moles of a monoprotic weak acid (Ka = 3.7 …

More Similar Questions