What is the pH after adding a base?

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Discussion Overview

The discussion revolves around calculating the pH of a solution after titrating a nitrous acid solution with barium hydroxide. Participants explore the necessary steps and concepts involved in determining the pH at a specific point in the titration process, including considerations of stoichiometry and buffer calculations.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant presents a titration scenario involving nitrous acid and barium hydroxide, expressing uncertainty about how to proceed after calculating moles of acid and base.
  • Another participant suggests that this is a classic buffer question and recommends using the Henderson-Hasselbalch equation after assuming neutralization goes to completion.
  • A follow-up inquiry seeks clarification on how to find the exact concentrations of the acid and conjugate base.
  • One participant emphasizes the importance of stoichiometry, indicating that knowing the amounts of acid and base allows for calculations of remaining acid and produced conjugate base, framing it as a limiting reagent question.
  • Another participant notes that the molarity of the acid and base is provided, linking molarity to concentration through the formula Molarity = Moles/Liter.
  • A caution is raised regarding the possibility of excess base, suggesting that if all acid is neutralized, the problem simplifies to a limiting reagent question.

Areas of Agreement / Disagreement

Participants generally agree on the relevance of stoichiometry and the use of the Henderson-Hasselbalch equation, but there is no consensus on the exact method to calculate the pH, as some participants express uncertainty and seek further clarification.

Contextual Notes

Participants mention various assumptions, such as the completion of neutralization and the potential for excess base, which may affect the calculations and the final pH determination.

megzb
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This is my question:
When a 17.9 mL sample of a 0.493 M aqueous nitrous acid solution is titrated with a 0.476 M aqueous barium hydroxide solution, what is the pH after 13.9 mL of barium hydroxide have been added?
I'm not really sure how to start it?
I have the moles of the acids and the base.
[acid]=8.8247E-3
[base]=6.6164E-3
but after that I'm lost! Help would be greatly appreciated!
 
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Classic buffer question. Assume neutralization went to completion, calculate concentrations of acid and conjugate base, use Henderson-Hasselbalch equation.

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Stoichiometry. You start with some amount of nitrous acid. You add some base. If neutralization went to completion, you are able to easily calculate amount of the acid left, and amount of conjugate base (product of the reaction) - this is just a limiting reagent question. You know amounts, you know the final volume - just plug and chug.

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methods
 
The molarity of your acid/base is given. Molarity = Moles/Liter IS your concentration.
 
Note: in case base is in excess all acid was neutralized, and it is just a limiting reagent question.

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