Equilibrium and Equivalence Calculation [Very Difficult]

[iBOOM]

Homework Statement

1. What volume of .022M HCl must be added to the 110ml buffer solution to completely react with the ammonia (NH₃) to reach equivalence. Then, what is the pH of this at the equivalence point.

Buffer solution (equilibrium): NH₃ + H₂0 ⇌ NH₄⁺ + OH^-
Other Info: .045M NH₄⁺ and .024M NH₃
and the pH of the buffer is 8.99
K_{b NH3} = 1.8 x 10^-5 Not sure if this is needed though.

Homework Equations

Molarity = n(moles)/V(volume in L)
pH = -log[H⁺]
Brackets means the concentration of the substance on the inside.
Not sure what else, I am sure there's some stoichiometry involved.

The Attempt at a Solution

I'm having a lot of trouble with this one.

 

[iBOOM]

So I've actually managed to do a bit but I'd really appreciate some help.

I've got the hydrolysis equation:
NH₃ + H⁺ <--> NH₄⁺
__.024M______.022M_______________.045M
__110ml________?ml________________110ml
.00264mol_________________________.00495mol

Do i just use stoichiometry to figure out the missing volume? And the equivalence, how does that play into the problem? Thanks in advance.

 

[iBOOM]

So I ended up doing some stoichiometry and got 120 ml of HCl required and then calculated the pH to 1.96. Can someone help me out?

 

[Borek]

This is a titration problem. Equivalence point is the moment when you should end the titration. You have a solution that contains ammonia (and some NH₄⁺ which we can for now safely ignore). How much HCl is needed to reach the equivalence point? This is a simple stoichiometry.

Next part is just a question about the equivalence point pH.