unit 13 acids and bases. properties electrolyte turn litmus red sour taste slippery feel turn litmus...
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Unit 13Unit 13
Acids and BasesAcids and Bases
Properties
• electrolyte
• turn litmus red
• sour taste• slippery feel
• turn litmus blue
• bitter taste• sticky feel
• electrolyte
• react with bases to form water and a salt (ionic compound)
• react with acids to form water and a salt (ionic compound)
ACIDS: Most citrus fruits, tea, battery acid, vinegar, milk, soda, apples.
BASES: Common household bases include baking soda, lye, ammonia, soap, and antacids.
.
Examples
Indicators
• Indicators are substances that change color in the presence of an acid or a base– Indicators are made up of weak acids or weak
bases– Examples of indicators include pH paper, red and
blue litmus paper, and phenolphthalein
Acids Affect Indicators:
Blue litmus paper turns red in contact with an acid. It remains blue when in contact with a base or neutral solution.
Bases affect indicators:
Red litmus paper turns blue in contact
with a base. It remains red when in contact with an acid or neutral solution.
Phenolphthalein turns pink in a
base. It is colorless in an acid or
neutral solution.
Definitions• There are 3 definitions used to
describe acids and bases:• Arrhenius
• BrØnsted-Lowry
• Lewis
• The most traditional is Arrhenius acids and bases.
Definitions
• ArrheniusArrhenius - In aqueous solution… - In aqueous solution…
HCl + H2O H+ + Cl–
– AcidsAcids form hydrogen ions (H+)
H
HH H H
H
ClClO O
–+
acid
Also called hydronium ions (H3O+)
Definitions
• ArrheniusArrhenius - In aqueous solution… - In aqueous solution…
– BasesBases form hydroxide ions (OH-)
NH3 + H2O NH4+ + OH-
H
H
HH H
H
N NO O–+
H
H
H H
base
Definitions
• Brønsted-LowryBrønsted-Lowry
HCl + H2O Cl– + H3O+
– AcidsAcids are proton (H+) donors. – BasesBases are proton (H+) acceptors.
conjugate acidconjugate basebaseacid
• ..
Conjugate acid – particle formed when a base gains a H+
Conjugate base – particle that remains when an acid has donated a H+
Another common way to refer to hydrogen ions is to call them
“protons”
Definitions
• LewisLewis– AcidsAcids are electron pair acceptors. – BasesBases are electron pair donors.
Lewis base
Lewis acid
White Board Questions1. When you wafted a substance your nose
burned. Would this substance be an acid or a base?
2. A hydrogen ion (H+) can also be called a _________ or ____________.
3. Arrhenius acids are compounds that break up in water to give off _____________.
4. What color litmus paper would you use to test an acid? What color will it turn?
5. If your food tastes bitter, which do you think it could possibly be an acid or a base?
ACID
H+
H3O+Proton
Blue turns red
BASE
White Board Questions6. A BrØnsted-Lowry base _________ hydrogen
ions.
7. Phenolphthalein turns pink when it comes in contact with a(n) _________.
8. Which of the scientists defined the typical acid?
9. If you are eating and it has a sour taste, would that be an acid or a base?
10. If a piece of red litmus paper turns blue than it is a(n) ___________.
accepts
base
Arrhenius
acid
base
Naming Acids
• Binary acids
– Contains 2 different elements: H and another
– Always has “hydro-” prefix
– Root of other element’s name
– Ending “-ic”
Examples of Binary Acids
• HI is hydroiodic acid
• H2S is hydrosulfuric acid
• HBr is hydrobromic acid
• HCl is hydrochloric acid
Naming Acids
• Ternary Acids - Oxyacids
– Contains 3 different elements: H, O, and another
– No prefix
– Name of polyatomic ion (p. 147)
– Ending “–ic” for polyatomic ion ending in “-ate” and “–ous” for ion ending in “-ite”
Examples of Ternary Acids
• ClO3 is chlorate so HClO3 is chloric acid
• PO4 is phosphate
so H3PO4 is phosphoric acid
• PO3 is phosphite
so H3PO3 is phosphorous acid
• NO2 is nitrite HNO2 is nitrous acid
• NO3 is nitrate HNO3 is nitric acid
Naming Acids cont.
• HC2H3O2 or CH3COOH
Name is acetic acid
Common name = vinegar
Practice Naming Acids
• H2SO3
– Sulfurous acid
• HF
– Hydrofluoric acid
• H2Se
– Hydroselenic acid
• Perchloric acid
– HClO4
• Carbonic acid
– H2CO3
• Hydrobromic acid
– HBr
Ion Product of WaterSelf- ionization of water – the simple dissociation of water
H2O H+ + OH-
Concentration of ea. ion in pure water: [H+] = 1.0 x 10-7M + [OH-] = 1.0 x 10-7M
Ion-product constant for water (Kw), Where KWhere Kww = 1.0 x 10 = 1.0 x 10-14-14
KKww = [H = [H++] [OH] [OH--]]
Acid [H+] > [OH-] Base [H+] < [OH-]
Neutral [H+] = [OH-]
Calculating [H+] and [OH-]
• reverse the pH equation
• The pH of a solution is 8. Find the [H+] and [OH-] and determine whether it is acidic, basic, or neutral.
– basic
[H+] = 1 x 10-pH and [OH-] = 1 x 10-pOH
[H+] = 1 x 10-8 M [OH-] = 1 x 10-(14-8) M = 1 x 10-6 M
Examples1. If the [H+] in a solution is 1.0 x 10-5M, is the
solution acidic, basic or neutral?
1.0 x 10-5 M
What is the concentration of the [OH-]?Use the ion-product constant for water (Kw):
Kw = [H+] [OH-] 1.0 x 10-14 = [1.0 x 10-5] [OH-] 1.0 x 10-14 = [OH-] 1.0 x 10-5
1.0 x 10-(14-5)
pH 5 = acidic
1.0 x 10-9 M
Examples2. If the pH is 9, what is the concentration of
the hydroxide ion?
Kw = [H+] [OH-]
1.0 x 10-14 M = [1.0 x 10-9M] [OH-]
1.0 x 10-5 M = [OH-]
3. If the pOH is 4, what is the concentration of the hydrogen ion?
Kw = [H+] [OH-]
1.0 x 10-14 M = [H+] [1.0 x 10-4 M]
1.0 x 10-10 M = [H+]
14 = pH + pOH
14 = 9 + pOH
5 = pOH
14 = pH + pOH
14 = pH + 4
10 = pH
Examples4. A solution has a pH of 4. Calculate the pOH,
[H+] and [OH-]. Is it acidic, basic, or neutral?
14= pH + pOH
14= 4 + pOH
10= pOH
–Acidic since pH is 4
M101][OH 10
M4101][H
Practice Problems:
Classify each solution as acidic, basic or neutral.
1. [H+] = 1.0 x 10-10 M
2. [H+] = 0.001M
3. [OH-] = 1.0 x 10-7 M
4. [OH-] = 1.0 x 10-4 M
Basic pH 101.0 x 10-3 acid pH 3
Neutral14=pH+4 base pH 10
[OH-] pOH pH [H+]
1 x 10-14 14 0 1 x 100
1 x 10-13 13 1 1 x 10-1
1 x 10-12 12 2 1 x 10-2
1 x 10-11 11 3 1 x 10-3
1 x 10-10 10 Increasing acidity 4 1 x 10-4
1 x 10-9 9 5 1 x 10-5
1 x 10-8 8 6 1 x 10-6
1 x 10-7 7 Neutral 7 1 x 10-7
1 x 10-6 6 8 1 x 10-8
1 x 10-5 5 9 1 x 10-9
1 x 10-4 4 Increasing basicity 10 1 x 10-10
1 x 10-3 3 11 1 x 10-11
1 x 10-2 2 12 1 x 10-12
1 x 10-1 1 13 1 x 10-13
1 x 100 0 14 1 x 10-14
White Board Practice Fill in the chart.
[OH-] pOH pH [H+]
8
1x 10-12
10
1 x 10-3
1.0 X 10 -8
1.0 X 10 -2
1.0 X 10 -4
1.0 X 10 -6
1.0 X 10 -10
1.0 X 10 -11
6
3 11
4
2 12
Fill in the chart.
[OH-] pOH pH [H+]
8
1x 10-12
10
1 x 10-3
5
1 × 10-1
1.0 X 10 -8
1.0 X 10 -2
1.0 X 10 -4
1.0 X 10 -6
1.0 X 10 -10
1.0 X 10 -11
6
3 11
4
2 12
9
113
1.0 X 10 -5 1.0 X 10 -9
1.0 X 10 -13
Strength or Concentration
• Strong Acid/BaseStrong Acid/Base– Ionize completely in water– strong electrolyte
- +
Acids
HCl
HNO3
H2SO4
HBr
HI
HClO4
Bases
NaOH
KOH
Ca(OH)2
Ba(OH)2
Strength or Concentration
• Weak Acid/BaseWeak Acid/Base– ionize partially in water– weak electrolyte
- +
Acids
HF
CH3COOH
H3PO4
H2CO3
HCN
Base
NH3
Strength or Concentration
• How strong or weak an acid or base is, depends on its degree of ionization.
- + - +
pH = -log[H+]
pH Scale
0
7INCREASING
ACIDITY NEUTRALINCREASING
BASICITY
14
pouvoir hydrogène (Fr.)“hydrogen power”
pH is the negative logarithm of the hydrogen ion concentration
The pH Scale
pH Scale
pH of Common SubstancespH of Common SubstancespH of Common SubstancespH of Common Substances
pH formulas
pH = -log[H+]
pOH = -log[OH-]
pH + pOH = 14
Neutralization
• Chemical reaction between an acid and a base.
• Products are a salt (ionic compound) and water.
Neutralization
ACID + BASE ACID + BASE SALT + WATER SALT + WATER
HCl + NaOH HCl + NaOH NaCl + H NaCl + H22OO
HCHC22HH33OO22 + NaOH + NaOH NaC NaC22HH33OO22 + H + H22OO
– Salts can be neutral, acidic, or basic.
– Neutralization does not mean pH = 7.
weak
strong strong
strong
neutral
basic
Titration
• TitrationTitration– Analytical method in
which a standard solution is used to determine the concentration of an unknown solution.
standard solution
unknown solution
• Equivalence point Equivalence point (endpoint)(endpoint)– Point at which equal amounts of H+
and OH- have been added.– Determined by…
• indicator color change
Titration cont.
• dramatic change in pH
Titration formula
moles H+ = moles OH-
MV n = MV n
M: MolarityV: volumen: # of H+ ions in the acid
or OH- ions in the base
Titration example
• 42.5 mL of 1.3M KOH are required to neutralize 50.0 mL of H2SO4. Find the molarity of H2SO4.
H2SO4
M = ?V = 50.0 mLn = 2
KOH
M = 1.3MV = 42.5 mLn = 1
MVn = MVnM(50.0mL)(2)=(1.3M)(42.5mL)(1)
M = 0.55M H2SO4
M= 55.25 100
Review of Acid and Base Definitions
• ArrheniusMost specific/exclusive definition
Created by Svante Arrhenius, Swedish
Acid: compound that creates H+ in an aqueous solution
HNO3 H+ + NO3-
Base: compound that creates OH- in an aqueous solution
NaOH Na+ + OH-
Review of Acid and Base Definitions
• Bronsted-LowryMore general definition than Arrhenius definition
Most commonly used definition
Created by 2 scientists around the same time (1923)
Acid: Molecule or ion that is a proton (H+) donor
HCl + H2O H3O+ + Cl-
Base: Molecule or ion that is a proton (H+) acceptor
NH3 + H2O NH4+ + OH-
Review of Acid and Base Definitions
• LewisMost general definition
Defined by electrons and bonding rather than H+
Created by the same scientist who electron-dot diagrams are named after
Acid: atom, ion, or molecule that accepts an electron pair to form a covalent bond
NH3 + Ag+ [Ag(NH3)2]+
Base: atom, ion, or molecule that donates an electron pair to form a covalent bond
BF3 + F- BF4-
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