Calculating pH: Vinegar and Ammonia Solution Equations

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Discussion Overview

The discussion revolves around calculating the pH of a solution after mixing vinegar and ammonia with water. Participants explore the necessary equations and concepts related to pH, particularly in the context of weak acids and bases. The focus is on understanding how to approach the problem rather than finding a definitive solution.

Discussion Character

  • Homework-related, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant seeks equations to calculate the pH after mixing vinegar (pH 2.4) with water (pH 7) and then adjusting the pH back to 7 using ammonia (pH 11.6).
  • Several participants inquire about the definition of pH, with one providing a formula: pH = -log [H+], emphasizing the importance of working with concentrations.
  • Another participant notes that both vinegar and ammonia are weak acid/base solutions, suggesting that simple concentration calculations may not suffice.

Areas of Agreement / Disagreement

There is no consensus on the specific equations or methods to use for the calculations, and multiple viewpoints on the definitions and implications of pH are presented.

Contextual Notes

Participants have not resolved the complexities involved in calculating pH for mixtures of weak acids and bases, and there are assumptions about the behavior of these substances that remain unaddressed.

Who May Find This Useful

This discussion may be useful for students studying chemistry, particularly those interested in acid-base reactions and pH calculations.

Blazzok
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Homework Statement


I need to know how to do the following. If I have 1L of water with a pH of 7 and I add 1mL Vinegar with a pH of 2.4, what will the pH of the solution then be?
I now need to get the pH of the solution back to 7 by adding ammonia which has a pH of 11.6. How much of that do I need to add?


I don't need a solution to the problem, i just need to know the equations so that i can solve this problem.
 
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What is the definition of pH?
 
CompuChip said:
What is the definition of pH?

pH = please Help?? -.-
 
Hehe, that's not a definition, it's a corollary :P

The pH of a solution is defined as -log [H+], minus the base-10 log of the concentration of H-ions. The trick is now to work with the concentrations. How many moles per litre do you have in both substances? How many when you put it together? Then how much is there in a litre of the new mixture?
 
Just don't forget vinegar and ammonia both mean weak acid/base, so just using concentration won't work.
 

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