Equilibrium and Equivalence Calculation [Very Difficult]

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Discussion Overview

The discussion revolves around a titration problem involving the calculation of the volume of hydrochloric acid (HCl) needed to reach the equivalence point with ammonia (NH3) in a buffer solution. Participants are also exploring the pH at the equivalence point, with a focus on stoichiometry and the relevant chemical equilibria.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant presents the initial problem, including the concentrations of NH4+ and NH3, and the pH of the buffer solution.
  • Another participant outlines the hydrolysis equation and attempts to use stoichiometry to find the missing volume of HCl needed for the reaction.
  • A different participant claims to have calculated the required volume of HCl as 120 ml and the resulting pH as 1.96, seeking further assistance.
  • Another participant clarifies that the equivalence point is when the titration should end and emphasizes the importance of stoichiometry in determining the amount of HCl needed.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and progress in solving the problem, with some uncertainty about the calculations and the role of stoichiometry. There is no consensus on the correct volume of HCl or the pH at the equivalence point, as different values have been proposed.

Contextual Notes

Participants have not fully resolved the stoichiometric calculations or the implications of the equivalence point on pH, and there are assumptions about the behavior of the buffer solution that remain unexamined.

Who May Find This Useful

Students or individuals studying chemistry, particularly those interested in titration problems and buffer solutions, may find this discussion relevant.

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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
Kb 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.
 
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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.
 
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?
 

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