Transcript 3. Ionization of Water
© 2013 Pearson Education, Inc.
General, Organic, and Biological Chemistry
Fourth Edition Karen Timberlake
Chapter 10
Acids and Bases
10.3
Ionization of Water Lectures
Ionization of Water
In
the ionization of water
, H + is transferred from one H 2 O molecule to another. one water molecule acts as an acid, while another acts as a base.
H 2 O(
l
) + H 2 O(
l
) H 3 O + (
aq
) + OH − (
aq
) © 2013 Pearson Education, Inc.
Chapter 10 Section 3 2
Ion Product of Water, K
w
The
ion product constant
,
K
w
, for water at 25 C is the product of the concentrations of the hydronium and hydroxide ions.
K
w = [ H 3 O + ][ OH − ] is obtained from the concentrations in pure water.
K K
w w = [ H 3 O + ][ OH − ] = [1.0 x 10 −7 M][1.0 x = 1.0 x 10 −14 © 2013 Pearson Education, Inc.
Chapter 10 Section 3 3
Pure Water is Neutral
In
pure water
, the ionization of water molecules produces small but equal quantities of H 3 O + and OH − ions.
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Chapter 10 Section 3 4
Acidic Solutions
Adding an
acid
to pure water increases the [H causes the [H 3 O 3 + O decreases the [OH + − exceed 1.0 x 10 −7 M.
], ], and ] to © 2013 Pearson Education, Inc.
Chapter 10 Section 3 5
Basic Solutions
Adding a
base
to pure water, increases the [OH decreases the [H 3 − ], O causes the [OH − ] to + exceed 1.0 x 10 −7 M.
], and © 2013 Pearson Education, Inc.
Chapter 10 Section 3 6
Comparison of [H
3
O
+
] and [OH
−
]
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Chapter 10 Section 3 7
[H
3
O
+
] and [OH
−
] in Solutions
In neutral, acidic, or basic solutions, the
K
w always 1.0 x 10 −14 .
at 25 C is © 2013 Pearson Education, Inc.
Chapter 10 Section 3 8
Guide to Calculating [H
3
O
+
] and [OH
−
]
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Chapter 10 Section 3 9
Calculating [H
3
O
+
]
What is the [H 3 O + ] of a solution if [OH − ] is 5.0 x 10 −8 M?
Step 1 Write the K w
K
w
for water.
= [H 3 O + ][OH − ]
Step 2 Solve the K w for the unknown [H 3 O + ].
[H 3 O + ] = 1.0 x 10 −14 [OH − ]
Step 3 Substitute the known [OH − ] into the equation and calculate.
[H 3 O + ] = 1.0 x 10 © 2013 Pearson Education, Inc.
Chapter 10 Section 3 10
Learning Check
If lemon juice has [H 3 O + ] of 2 x 10 −3 of the solution?
M, what is the [OH − ] A. 2 x 10 −11 M B. 5 x 10 −11 M C. 5 x 10 −12 M © 2013 Pearson Education, Inc.
Chapter 10 Section 3 11
Solution
If lemon juice has [H 3 O + ] of 2 x 10 −3 of the solution?
M, what is the [OH − ]
Step 1 Write the K w
K
w
for water.
= [H 3 O + ][OH − ] = 1.0 x 10 −14
Step 2 Step 3 Solve the K w for the unknown [OH
[OH − ] = 1.0 x 10 −14
− ].
[H 3 O + ]
Substitute the known [H 3 O + ] into the equation and calculate.
[2 x 10 −3 ] Answer is C.
Chapter 10 Section 3 © 2013 Pearson Education, Inc.
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