pH 2016 fileld in.notebook
May 10, 2016
pH ­ Potential of Hydrogen Ions
Aim: pH and hydronium ion concentration concentration.
Mar 25­5:20 PM
pH scale measures the H+ concentration in a given sample
Acids have a more [H3O+] than [OH­] and a pH range of 0­7
­The lower the pH, the stronger the acid.
pH= 6
vs.
pH= 1
Bases have a less [H3O+] than [OH­] and a pH range of 7­14.
­The higher the pH, the stronger the base.
Mar 25­5:24 PM
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pH 2016 fileld in.notebook
May 10, 2016
Neutral Solutions
A neutral solution has a pH of 7
In a solution that is neutral the [H+] = [OH­]
[H+]= 1 x10­7 therefore the pH=7
Mar 25­6:25 PM
Converting from [H+] to pH
The concentration of H3O+ ions is measured in scientific notation.
The exponent on the 10 of H3O+ concentration is the pH
[H+] = 1 x 10­pH
[H3O+] = __1 x 10­5____________ pH= _5__acidic_
What is the pH of solutions below?
a) 1 x 10­11
basic
­pH=11
b) 1 x 10­5 pH=5
acidic
Mar 25­6:07 PM
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pH 2016 fileld in.notebook
May 10, 2016
From pH to [H+]
Oppositely, the pH value can be used as the exponent on the 10 for the H3O+ concentration
What is the [H3O+] of a solution that has a pH of 6?
[H3O+]= __1 x 10­6_________
Determine the [H3O+] concentration of solutions with the following pH values:
a) pH = 12 [H3O+]= __1 x 10­12_____________
b) pH = 7 [H3O+]= ___1 x 10­7____________
Mar 25­6:18 PM
Changing pH
Changing the pH by 1 changes the concentration by a factor of 10.
pH 1 to a pH 4
­ becomes less acidic
[H+] = 1 x 10­1 to [H+] = 1 x 10­4
H+ conc. decreases by 103, 1000 fold.
pH 8 to a pH 6
­becomes more acidic
[H+] = 1 x 10­8 to [H+] = 1 x 10­6
H+ conc. increases by 102, 100 fold.
Mar 27­6:02 PM
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pH 2016 fileld in.notebook
May 10, 2016
Determine the pH of each solution below given the H+ concentration:
a) [H+]= 10­9 pH = ________ Acidic or Basic
b) [H+]= 10­3 pH = ________ Acidic or Basic
Determine the [H+] of the solution given the pH:
c) pH=5 [H+] = ___________ Acidic or basic
d) pH= 10 [H+] = __________Acidic or basic
Mar 25­6:39 PM
Amphoteric Amphoteric: A substance that may act as both an acid or base is called amphoteric
H2O(l) + H2O(l) ↔ H3O+ (aq) + OH­(aq)
Water is amphoteric and can act as a base OH­ or an acid H3O+ and will be in equilibrium with these two ions. This is why the pH is neutral, 7.
Mar 25­9:56 AM
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