Hydrogen Ions and Acidity

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20.1

• Hydrogen Ions and Acidity

I pity the fool who does not know how to do pH
calculations!
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Self-ionization - the reaction in which two water
molecules produce ions
H2O --gt H OH- Water
Hydrogen ion hydroxide ion
H2O H2O --gt H30
OH- Water Water Hydronium
ion hydroxide ion
Pure Water neutral solution
H30 1.0 x 10-7 M OH- 1.0 x 10-7 M
Kw ion-product constant for water Kw H30
OH- 1.0 x 10-14 M
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Remember LeChatelier?? What happens to the H
concentration when the OH- concentration
increases?
H2O lt--gt H OH-
Acidic when H is greater than OH-
Basic when OH- is greater than H
AKA Alkaline solution
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Use the Kw expression to solve the following
Kw H30 OH- 1.0 x 10-14 M
1. What is H30 equal to if OH- is 1.9 x10-2
M?
2. What is the hydroxide concentration if the
hydronium concentration is 5.1 x10-9 M?
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pH scale used to measure how acidic or basic a
solution is
pH - log H30
Acid pH lt 7.0 H30 gt 1 x
10-7 Neutral pH 7.0 H30 1 x
10-7 Base pH gt 7.0 H30 lt 1 x
10-7
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Equations for all pH and related problems...
pH - log H30 pOH - log OH- H30 inv
log (-pH) OH- inv log (-pOH) pH pOH
14 H30 OH- 1.0 x 10-14 M
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Complete the following table using the equations
on the previous slide
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Acid / Base Indicators
HIn lt--gt H In- acid
form base form
Use LeChatelier to determine which direction the
reaction will shift...
More Hreaction shifts __________
Less Hreaction shifts __________