Transcript Acids, Bases, and Salts

Acids and Bases
http://www.unit5.org/chemistry/AcidBase.html
Concentration vs. Strength
Concentrated vs. Dilute
Strong vs. Weak
Acids: Concentration vs. Strength
WEAK
STRONG
CONCENTRATED
H+ A- H+ A- H+ A- H+ A- HA
A- H+ A- H+ A- H+ A- H+ A H+ A- HA H+ A- H+ A- H+ AA- H+ A- H+ A- H+ A- H+ A- H+
H+ A - H + A - H + A - HA H + A A- H+ A- H+ A- H+ A- H+ A–
H+ A- H+ A- H+ A- H+ A- H+
A- H+ A- H+ A- H+ A- H+ AHA A- H+ A- H+ A- H+ A- H+
HA HA H+ A- HA HA
HA HA HA HA HA
H+ A- HA HA HA HA
HA HA H+ A- HA HA
HA HA HA H+ A- HA
H+ A- HA HA HA HA
HA HA HA H+ A- HA
H+ A- HA HA HA HA
HA HA H+ A- HA HA
HA
H+ AHA
HA
HA
HA
HA
HA
HA
DILUTE
H+
A-
H+
A-
HA
A-
H+
A-
H+
A–
H+
A-
H+
A-
H+
A-
H+
HA
H+
A-
HA
H+
HA
A-
HA
HA
HA
H+ A -
HA
HA
HA
HA
H+A–
A-
Dissociate nearly 100%
HA
H1+
+
A-
+
A-
H+
HA
HA
HA
H+A–
HA
STRONG ACIDS
HA
WEAK ACIDS
Dissociate very little
HA
H1+
Strong vs. Weak Acid
Strength DOES NOT mean concentration
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 508
pH Scale
Søren Sorensen
(1868 - 1939)
Basic
7
Acid
pH is a way to
measure the
strength of an acid
or base.
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 515
14
Neutral
pH Scale
Acidic
0
Base
[H+]
pH
10-14
14
10-13
13
10-12
12
10-11
11
10-10
10
10-9
9
10-8
8
10-7
7
10-6
6
10-5
5
10-4
4
10-3
3
10-2
2
10-1
1
100
0
1 M NaOH
Ammonia
(household
cleaner)
Blood
Pure water
Milk
Vinegar
Lemon juice
Stomach acid
1 M HCl
pH of Common Substances
gastric
juice
1.6
vinegar
2.8
carbonated
beverage
3.0
0
1
2
acidic
Timberlake, Chemistry 7th Edition, page 335
urine
6.0
4
5
bile
8.0
6
7
neutral
[H+] = [OH-]
8
ammonia
11.0
bleach
12.0
seawater
8.5
9
1.0 M
NaOH
(lye)
14.0
milk of
magnesia
10.5
detergents
8.0 - 9.0
milk
6.4
tomato
4.2
coffee
5.0
3
blood
7.4
potato
5.8
apple juice
3.8
lemon
juice
2.2
drinking water
7.2
bread
5.5
orange
3.5
1.0 M
HCl
0
water (pure)
7.0
soil
5.5
10
11
basic
12
13
14
pH of Common Substance
More acidic
More basic
pH
NaOH, 0.1 M
Household bleach
Household ammonia
Lime water
Milk of magnesia
Borax
Baking soda
Egg white, seawater
Human blood, tears
Milk
Saliva
Rain
Black coffee
Banana
Tomatoes
Wine
Cola, vinegar
Lemon juice
Gastric juice
14
13
12
11
10
9
8
7
76
5
4
3
2
1
0
[H1+]
[OH1-]
pOH
1 x 10-14
1 x 10-13
1 x 10-12
1 x 10-11
1 x 10-10
1 x 10-9
1 x 10-8
1 x 10-7
1 x 10-6
1 x 10-5
1 x 10-4
1 x 10-3
1 x 10-2
1 x 10-1
1 x 100
1 x 10-0
1 x 10-1
1 x 10-2
1 x 10-3
1 x 10-4
1 x 10-5
1 x 10-6
1 x 10-7
1 x 10-8
1 x 10-9
1 x 10-10
1 x 10-11
1 x 10-12
1 x 10-13
1 x 10-14
0
1
2
3
4
5
6
8
9
10
11
12
13
14
Acid – Base Concentrations
concentration (moles/L)
10-1
pH = 3
pH = 11
OH-
H3O+
pH = 7
10-7
H3O+
OH-
OH-
H3O+
10-14
Timberlake, Chemistry 7th Edition, page 332
[H3O+] > [OH-]
[H3O+] = [OH-]
acidic
solution
neutral
solution
[H3O+] < [OH-]
basic
solution
pH
pH = -log [H1+]
Kelter, Carr, Scott, Chemistry A World of Choices 1999, page 285
pH Calculations
pH
pH = -log[H3O+]
[H3O+]
[H3O+] = 10-pH
[H3O+] [OH-] = 1 x10-14
pH + pOH = 14
pOH
pOH = -log[OH-]
[OH-]
[OH-] = 10-pOH
pH = - log [H+]
Given: pH = 4.6
pH = - log [H+]
choose proper equation
4.6 = - log [H+]
substitute pH value in equation
- 4.6 =
2nd
log
determine the [hydronium ion]
- 4.6 =
log [H+]
log [H+]
[H+] = 2.51x10-5 M
multiply both sides by -1
take antilog of both sides
Recall, [H+] = [H3O+]
10x
antilog
You can check your answer by working backwards.
pH = - log [H+]
pH = - log [2.51x10-5 M]
pH = 4.6
pH Indicators
Substances that change color depending on the
pH of the solution..
Litmus Paper
Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.
pH Paper
pH 0
1
2
3
4
5
6
pH 7
8
9
10
11
12
13
Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.
Desired Features of Sensors
pH paper
1904
pH 0
1
2
3
4
5
pH 7
8
9
10
11
12
6
13
Detection limit
Low deflection
High sensitivity
High selectivity
Wide dynamic
range
Simple to use
Cost-effective
Range and Color Changes of Some
Common Acid-Base Indicators
pH Scale
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Indicators
Methyl orange
Methyl red
Bromthymol blue
Neutral red
Phenolphthalein
3.1 – 4.4
red
red
4.4
yellow
yellow
6.2
6.2
red
colorless
6.8
yellow
7.6
8.0
8.0
blue
yellow
10.0
red
Bromthymol blue indicator would be used in titrating a strong acid with a strong base.
Phenolpthalein indicator would be used in titrating a weak acid with a strong base.
Methyl orange indicator would be used in titrating a strong acid with a weak base.
colorless beyond 13.0
pH
Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.
INDICATOR COLORS IN TITRATION
Indicator
Acid color
Transition color
Base color
STRONG ACID – STRONG BASE
Litmus
2
pH
Bromthymol blue
3
4
5
6
7
8
9
10
11
12
INDICATOR COLORS IN TITRATION
Indicator
Acid color
Transition color
Base color
WEAK ACID – STRONG BASE
Phenolphthalein
2
pH
Phenol red
3
4
5
6
7
8
9
10
11
12
INDICATOR COLORS IN TITRATION
Indicator
Acid color
Transition color
Base color
STRONG ACID – WEAK BASE
Methyl orange
2
pH
Bromphenol blue
3
4
5
6
7
8
9
10
11
12
Indicator
1
2
Orange IV
phenolphthalein
4
5
Colorless
Phenolphthalein
Methyl Red
3
pH
6 7 8
Red
Orange
Peach
methyl red
Orange
9 10 11 12
Pink
Red
Yellow
Yellow
methyl orange
Common pH Indicators
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 520
Edible Acid-Base Indicators
COLOR CHANGES AS A FUNCTION OF pH
INDICATOR
pH
2
3
4
5
6
7
8
9
10
11
12
RED APPLE SKIN
BEETS
BLUEBERRIES
RED CABBAGE
*
CHERRIES
GRAPE JUICE
RED ONION
YELLOW ONION
PEACH SKIN
PEAR SKIN
PLUM SKIN
RADISH SKIN
RHUBARB SKIN
TOMATO
TURNIP SKIN
*YELLOW at pH 12 and above
Red Cabbage Indicator
Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.
H+
Phenolphthalein
Indicator
Colorless = Acidic pH
Pink = Basic pH
-O
O
C
C
OH
HO
C
O-
O
(Colorless acid form, HIn)
C
OH
O-
O
(Pink base form, In-)