Properties of AcidsProperties of Acids Taste sour (don’t try this at Taste sour (don’t try this at
home).home). Conduct electricity.Conduct electricity.
–Some are strong, others are weak electrolytes.
Properties of AcidsProperties of Acids React with metals to form React with metals to form
hydrogen gas.hydrogen gas. Change indicators (blue Change indicators (blue
litmus to red).litmus to red). React with hydroxides to React with hydroxides to
form water and a salt.form water and a salt.
Properties of BasesProperties of Bases
React with acids to form water React with acids to form water and a salt.and a salt.
Taste bitter.Taste bitter. Feel slippery (don’t try this Feel slippery (don’t try this
either).either).
Names and Formulas of AcidsNames and Formulas of Acids An acid is a chemical that An acid is a chemical that
produces hydrogen ions produces hydrogen ions (H(H1+1+) when dissolved ) when dissolved in in waterwater
Thus, general formula = HX, Thus, general formula = HX, where X is a monatomic or where X is a monatomic or polyatomic anionpolyatomic anion
Names and Formulas of AcidsNames and Formulas of Acids
HClHCl(g)(g) named hydrogen named hydrogen chloridechloride
HClHCl(aq)(aq) is named as an acid is named as an acid Name focuses on the Name focuses on the
anion presentanion present
Names and Formulas of AcidsNames and Formulas of Acids
1. When anion ends with -1. When anion ends with -ide, the acid starts with ide, the acid starts with hydro-,hydro-, and the stem of and the stem of the anion has the suffix the anion has the suffix --icic followed by the word followed by the word acidacid
Names and Formulas of AcidsNames and Formulas of Acids2. When anion ends with -ite, 2. When anion ends with -ite, the anion has the suffix the anion has the suffix -ous-ous, , then then acidacid
3. When anion ends with -ate, 3. When anion ends with -ate, the anion suffix is the anion suffix is -ic-ic and then and then acidacid
Table 19.1, page 588 for Table 19.1, page 588 for examplesexamples
Names and Formulas of BasesNames and Formulas of Bases A base produces A base produces
hydroxide ions (OHhydroxide ions (OH1-1-) ) when dissolved when dissolved in waterin water..
Named the same way as Named the same way as any other ionic compoundany other ionic compound–name the cation, followed by
anion
Names and Formulas of BasesNames and Formulas of Bases To write the formula: To write the formula:
write symbols; write write symbols; write charges; then cross (if charges; then cross (if needed)needed)
Hydrogen Ions from WaterHydrogen Ions from Water Water ionizes, or falls apart Water ionizes, or falls apart
into ions:into ions:H2O H1+ + OH1-
Called the “self ionization” of Called the “self ionization” of waterwater
Occurs to a very small extent:Occurs to a very small extent:[H1+ ] = [OH1-] = 1 x 10-7 M
Hydrogen Ions from WaterHydrogen Ions from Water Since they are equal, a Since they are equal, a
neutralneutral solution results solution results from waterfrom water
KKww = [H = [H1+1+ ] x [OH ] x [OH1-1-] = 1 x ] = 1 x 1010-14-14 M M22
KKww is called the is called the “ion product constant”“ion product constant”
Ion Product ConstantIon Product Constant HH22O O H H++ + OH + OH--
KKww is constant in every is constant in every aqueous solution: aqueous solution: [H [H++] x [OH] x [OH--] = 1 x ] = 1 x 1010-14 -14 MM22
If [HIf [H++] > 10] > 10-7-7 then [OH then [OH--] < 10] < 10-7-7 If [HIf [H++] < 10] < 10-7-7 then [OH then [OH--] > 10] > 10-7-7
Ion Product ConstantIon Product Constant If we know one, other can be If we know one, other can be
determineddetermined If [HIf [H++] > 10] > 10-7 -7 , ,
it is it is acidicacidic and and [OH[OH--] < 10] < 10-7-7
If [HIf [H++] < 10] < 10-7 -7 , , it is it is basicbasic and [OH and [OH--] > ] > 1010-7-7
Basic solutions also called Basic solutions also called “alkaline”“alkaline”
ExampleExample
[H+] = 1 x 10[H+] = 1 x 10-5-5 M M
Acid, Base Acid, Base or Neutralor Neutral
1010-5-5 > 10 > 10-7-7
AcidicAcidic
The pH conceptThe pH concept Logarithms are powers of Logarithms are powers of
ten.ten. definition: definition:
pH = pH = -log[H-log[H++]] in neutral in neutral
pH = pH = -log(1 x 10-log(1 x 10-7-7) = 7) = 7 in acidic solution [Hin acidic solution [H++] > 10] > 10-7 -7
in basic solution [Hin basic solution [H++] < 10] < 10-7 -7
The pH conceptThe pH concept pH pH < -log(10< -log(10-7-7)) pH < 7 pH < 7
(0 to 7 is the (0 to 7 is the acidacid range)range)
in base, pH > 7 in base, pH > 7 (7 to 14 is (7 to 14 is base base range)range)
pH and pOHpH and pOH pOH = -log [OHpOH = -log [OH--] ] [H[H++] x [OH] x [OH--] = 1 x 10] = 1 x 10-14 -14 MM22
pH + pOH = 14pH + pOH = 14 Thus, a solution with a pOH Thus, a solution with a pOH
less than 7 is basic; with a less than 7 is basic; with a pOH greater than 7 is an pOH greater than 7 is an acidacid
0 1 3 5 7 9 11
13
140135791
113
14
Basic
100
10-
1
10-
3
10-
5
10-
7
10-
9
10-
11
10-
13
10-
14
Basic
100
10-
1
10-
3
10-
5
10-
7
10-
9
10-
11
10-
13
10-
14
Acidic Neutral
[OH-]
pH
[H+]
pOH
What is the pH of a solution with H–What is the pH of a solution with H–ion concentration of 4.2 X 10ion concentration of 4.2 X 10-10-10M.M.
pH = -log [H+]pH = -log [H+]pH = -log (4.2 X 10pH = -log (4.2 X 10-10-10))
pH = -(log 4.2 + log 10pH = -(log 4.2 + log 10-10-10]]
pH = -(0.645 + (-10))pH = -(0.645 + (-10))
pH = -(0.645 + (-10))pH = -(0.645 + (-10))
pH = 9.38 AlkalinepH = 9.38 Alkaline
pH is 6.35, what is the H–ion pH is 6.35, what is the H–ion concentration?concentration?
pH = -log [H+]pH = -log [H+]-log [H+] = 6.34-log [H+] = 6.34
log [H+] = -6.34log [H+] = -6.34
[H+] = 10 [H+] = 10 -6.34-6.34
[H+] = 4.5 X 10[H+] = 4.5 X 10-7-7 M M
Measuring pHMeasuring pH Why measure pH?Why measure pH?
–Everything from swimming pools, soil conditions for plants, medical diagnosis, soaps and shampoos, etc.
Sometimes we can use Sometimes we can use indicators, other times we indicators, other times we might need a pH metermight need a pH meter
Acid-Base IndicatorsAcid-Base Indicators An indicator is an acid or base An indicator is an acid or base
that undergoes dissociation in that undergoes dissociation in a known pH range, and has a known pH range, and has different colors in solution different colors in solution (more later in chapter)(more later in chapter)
Examples: litmus, Examples: litmus, phenolphthalein, bromthymol phenolphthalein, bromthymol blue: Fig 20.8, p.590blue: Fig 20.8, p.590
Acid-Base IndicatorsAcid-Base Indicators A A pH meterpH meter may give more may give more
definitive resultsdefinitive results–some are large, others portable
–works by measuring the voltage between two electrodes
–needs to be calibrated
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