Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: eeyore1228 on June 29, 2005, 04:00:55 PM
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A solution is prepared by adding some unknown amount of sodium hydroxide to a volumetric flsk and diluting the solution to 250.0 mL. You measure the pH using a pH meter to be 12.4. What is the hydronium ion concentration?
What is the hydroxide concentration?
I do not understand how to convert a given pH into the ion concentration. I know that the OH- and the H3O+ together needs to be 14.
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Remember that pH is equal to the negative 10-base log of the hydrogen ion concentration.
pH = - log [H+ ]
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Look here for definition and some very basic stuff about pH:
http://www.chembuddy.com/?left=pH-calculation&right=introduction-acid-base-equilibrium (http://www.chembuddy.com/?left=pH-calculation&right=introduction-acid-base-equilibrium)
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Alright, so pH = -log [H3O+] is how to figure out pH from the [].
To figure it out the other way around from [H3O+] to pH you would go:
[H3O+] = 10^-pH
The hydronium ion concentration is equal to 10 to the power of the negative pH.
Example: What is the [H3O+] in a solution with pH = 2.
[H3O+] = 10^-pH
= 10^(-2)
= 0.01 M