PH: product of concentration of H+ and OH-

Click For Summary

Homework Help Overview

The discussion revolves around the relationship between the concentrations of hydrogen ions \([H^+]\) and hydroxide ions \([OH^-]\) in water, specifically addressing the equation \([H^+][OH^-]=10^{-14}\) and its implications for pH and pOH values.

Discussion Character

  • Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants explore the reasoning behind the equation relating \([H^+]\) and \([OH^-]\), with some questioning the conditions under which it holds true. Others clarify the relationship between pH, pOH, and the product of ion concentrations.

Discussion Status

The discussion is active, with participants providing clarifications and mathematical reasoning regarding the relationship between pH and the concentrations of ions in water. There is an acknowledgment of the context of standard conditions for water, and some participants are exploring different interpretations of the original question.

Contextual Notes

Some participants note the lack of specific conditions or substances in the original post, which may affect the interpretation of the equation. The discussion is framed around the properties of water at standard conditions.

amcavoy
Messages
663
Reaction score
0
Why is the following true?:

[tex]\left[H^+\right]\left[OH^-\right]=10^{-14}[/tex]

It seems like they would cancel out (equal 10-7 instead). Thanks for your help.
 
Physics news on Phys.org
What substance are you talking about? pH depends on many factors and you give none. How ever if you are talking about water at standard conditions then it does indeed cancel out to 10^-7.
 
It does not equal [itex]10^{-7}[/itex].

The [itex]pH[/itex] of water is 7, and so is the [itex]pOH[/itex].

[itex]pH+pOH=7+7=14[/itex]

[itex]-log[H^+]-log[OH^-]=14[/itex]

[itex]-log([H^+][OH^-])=14[/itex]

[itex]log([H^+][OH^-])=-14[/itex]

Exponentiating both sides in base 10 gives you the result in the opening post. That result holds true no matter how acidic or how basic your solution gets.
 
Last edited:
Ok thanks. I didn't realize it was for water when I looked at it.
 

Similar threads

Electron and hole concentration
  • · Replies 1 ·
Replies
1
Views
2K
Chemistry Comparing methods of computing pH at equivalence point in titration
  • · Replies 4 ·
Replies
4
Views
2K
Chemistry How to take into account autoprotolysis in weak base solution?
  • · Replies 8 ·
Replies
8
Views
3K
Henderson Hasselbalch Equation - Request for Clarification
  • · Replies 8 ·
Replies
8
Views
3K
Use linear regression to find Planck’s constant
  • · Replies 10 ·
Replies
10
Views
2K
Something that doesn't make sense to me about calculating the pH
  • · Replies 14 ·
Replies
14
Views
4K
Chemistry Finding the pH of this acid and its sodium salt solution
  • · Replies 7 ·
Replies
7
Views
3K
Calculating pKa from pH: Understanding Titration
  • · Replies 3 ·
Replies
3
Views
4K
Force to apply to a loop moving away from a current-carrying wire
  • · Replies 4 ·
Replies
4
Views
2K
Constant Pressure Specific Heat in terms of Entropy and Enthelpy
  • · Replies 11 ·
Replies
11
Views
2K