unit 14/15/16 – acids, bases & salts
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Unit 14/15/16 – Acids, Bases & Salts. Electrolytes: Faraday: defined electrolytes/ nonelectrolytes ElectrolytesNon electrolytes 1. conduct elect.1. non conductor 2. ions + & -2. molecules (neutral) 3. cation +, anion -3. organic (covalent) Ex: HCl Ex: alcohol - PowerPoint PPT PresentationTRANSCRIPT
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Unit 14/15/16 – Acids, Bases & SaltsElectrolytes:
• Faraday: defined electrolytes/ nonelectrolytes
Electrolytes Non electrolytes
1. conduct elect. 1. non conductor
2. ions + & - 2. molecules (neutral)
3. cation +, anion - 3. organic (covalent)
Ex: HCl Ex: alcohol
NaOH sugar
NaCl glycerol
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• Arrhenius: defined Acid/Base/Salt as made of Ions
1. Acids: H+ (hydrogen ions)
2. Bases: OH- (hydroxide ions)
3. Salts: made of + ions (mostly metals) and
-- ions (not OH-)
• Bronsted –Lowrey: ions in aqueous solution
1. Acids: H3O+ ; H+ + HOH H3O+
(hydronium ion) proton donor
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2. Bases: OH- (hydroxide ion) proton acceptor
3. Salts: + cation & - anion, (no OH-)
• Lewis: broadest definition – e- pair exchange
1. Acids: electron pair acceptors
2. Bases: electron pair donors
3. Salts: + cations & - anions, no constraints
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Dissociation of ionic compounds:
falls apart, strong electrolytes in HOH solution (aqueous)
Ionization of ionic compounds:
Pulled (ripped) apart by HOH in aqueous solution, weak electrolytes
Examples:
Acids: HCl H3O+ + Cl-
Bases: NaOH Na+ + OH-
Salts: NaCl Na+ + Cl-
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Symbolic representations
Solids (precipitates): (s), (c), ppt,
Ions: H+, H3O+, OH-, M+, Nm-, polyatomic + or –
Equilibrium:
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Acids: chemical compounds that dissociate to H3O+ & Nm- (Arrhenius H+, Bronsted H3O+)
1. Donate H+ or H3O+ ions2. pH < 7 3. Corrosive
4. Caustic (eat away)
5. Toxic, Some poisonous (H3PO4, HF)6. React with metals7. Affect indicators 8. feel wet9. neutralize bases 10. Taste sour
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- Mineral Acids contain H3O+ ions
1. HCl
2. HBr
3. HClO3
4. HClO4
5. HNO3
6. H2CO3
7. H2SO4
8. H3PO4
9. H2SeO4
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- Organic (carboxyl) acids contain COOH--
1. Formic acid – produced by red ants
2. Citric acid – grapefruits, oranges
3. Ascorbic acid – tomato, vitamin C
4. Lactic acid - milk
5. Buteric acid – rancid butter, cheese
6. Acetic acid – fruits, grains - vinegar
7. Malic acid – apples, pears
8. Acetylsalicylic –willow tree bark aspirin
9. Oxalic –sorrel plant
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Bases: chemical compounds that dissociate to M+ and OH-
1. Hydroxide (OH-) ions
2. pH > 7
3. Slippery feeling
4. Affect indicators
5. Neutralize acids
6. toxic 7. electrolytes 8. corrosive (metals)
9. caustic (skin) 10. Bitter taste
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Mineral Organic
1. LiOH 1. methanol- paint thinner
2. NaOH - lye 2. ethanol – medical
3. KOH 3. propanol – rubbing alcohol
4. RbOH 4. butanol
5. CsOH 5. pentanol
6. NH4OH-ammonia 6. hexanol
7. Mg(OH)2-mom 7. heptanol
8. Ca(OH)2-lime 8. octanol
9. Sr(OH)2 9. nonanol
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10. Ba(OH)2 10. decanol
11. Al(OH)3 11. ethyl glycol- anti freeze
12. Zn(OH)2 12. glycerol – medical syrup
Important acids:Hydrochloric acid – HClExtremely soluble in HOH dilution 4:135% strong acidSpecific gravity 1.20
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Uses (HCl):
1. Pickling metals (purify steel)
2. Preparation for Mg
3. Cleaning
Sulfuric acid – H2SO4
1. 95 to 98% pure
2. dense, oily
3. dilution 6:1(water to acid)
4. Spgr 1.84
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Uses (H2SO4):
1. cellulose (film)
2. Fertilizers
3. Processing metal
4. Refining oil
Nitric acid – HNO3 (Dangerous, not in HS)
1. 68% pure (unstable), turn brown gradually
2. dilution 5:1 (water to acid)
3. Volatile 4. Spgr 1.42
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Uses (HNO3):
1. Fertilizers 3. dyes
2. Explosives 4. plastics
Phosphoric acid – H3PO4
1. weak acid
2. dilution 2:1 (water to acid)
3. 88%
4. Spgr 1.87
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Uses (H3PO4):
1. Fertilizers 3. rust proofing
2. detergents 4. phosphorous compounds
Acetic acid – HC2H3O2
1. Pungent
2. 99.8%
3. Dilution 8:1 (water to acid)
4. Spgr 1.05
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Uses (HC2H3O2):
1. Plastics
2. Foods
3. Disinfectant in cleaning
Important Bases:
Lye – NaOH
1. Solid white 3. toxic
2. 97-98% 4. Spgr 1.06
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Uses (NaOH):
1. Plastics 3. cellulose film
2. Soap 4. neutralize acid
Lime- Ca(OH)2:
1. Solid white 3. caustic
2. Toxic
Uses:
1.Water softner 3. plastics
2. Odor control 4. lawns
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MOM – Mg(OH)2:
1. Solid white
2. Absorb CO2
3. Colloid
Uses:
1. Neutralize acids
2. Stomach upsets (anti acids)
3. Sunburns
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Properties of Electrolytes:Acids:
1. Electrolytes H3O+
2. Dissociate completely3. Single HOH4. Dangerous even dilutedBases:1. Electrolytes OH-
2. Dissociate completely3. Single HOH4. Dangerous even diluted
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Weak Electrolytes:
Acid/Base/Salt:
1. Weak acids and bases
2. Partially ionize
3. Minimum caustic but may be toxic
4. Equilibrium
Examples:
Strong Acids:
1. HCl 2. HBr 3. HI 4. HNO3
5. HClO3 6. HClO4 7. H2SO4 8. H2SeO4
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Strong Bases:
1. NaOH 2. KOH 3. CsOH
4. Ca(OH)2 5. Sr(OH)2 6. Ba(OH)2
Weak Acid/Base/Salt:
1. H3PO4 2. H2CO3 3. HC2H3O2
4. LiOH 5. Mg(OH)2 6. Zn(OH)2
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Anhydride: without HOH/ anhydrous
Acid Anhydride: nonmetal oxide NmO
Ex: CO2 + HOH H2CO3
SO2 + HOH H2SO3
Basic Anhydride: metal oxides MO(alkaline)
Ex: K2O + HOH 2 KOH
CaO + HOH Ca(OH)2
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Conjugate pairs: the species that remain after an acid/base given up/taken on a proton.
Ex:
weaker weaker stronger stronger
1. HC2H3O2 + HOH H3O+ + C2H3O2-
acid base acid base
stronger stronger weak weak
2. HClO4 + HOH H3O+ + ClO4-
acid base acid base
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Amphoteric Compounds: maybe an acid or base depends on situation. Weak acid acts as a base, weak base acts as an acid, and weak/neutral acts as an acid or a base.
Ex: A1(OH)3 Pb(OH)2 Sn(OH)2
Using the Periodic Chart for A/B/S
Ex: 1. Li 2. Cl 3. Zn 4. Al
5. Sr 6. Br 7. Ag 8. Sn
9. K 10. S
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Acid/Base Reaction:
Acid:
1. A + B Salt + HOH
2. A + Carbonate Salt + HOH + CO2
3. A + metal Salt + H2
4. HOH + nonmetal oxide Acid
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Base:
1. B + nonmetal oxide Salt + HOH
2. HOH + metal oxide B
Salt:
1. Metal oxide + nonmetal oxide Salt
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Protic acids:
1. Monoprotic: one H+ proton
HCl, HBr, HC2H3O2, HClO3, HNO3
2. Diprotic: 2 H+
H2SO4, H2CO3, H2SeO4, H2SO3, H2BrO3
3. Triprotic: 3 H+
H3PO3, H3PO4, H3AsO4
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Self Ionization: 2 water molecules
HOH + HOH H3O+ + OH-
Power of Hydrogen
Definition: negative log of [H3O+]
1. Vinegar pH – 2.8
2. Distilled waterpH – 7.0
3. MOM pH – 10.5
Hydronium: H3O+ Hydroxide: OH-
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Strong Acids Strong Bases
1. HCl 1. NaOH
2. HBr 2. KOH
3. HI 3. CsOH
4. HNO3 4. Ca(OH)2
5. HClO4 5. Sr(OH)2
6. HClO3 6. RbOH
7. H2SO4 7. Ba(OH)2
8. H2SeO4
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Calculating pH
Formula: pH = - log [H3O+]
Calculating pOH
Formula: pOH = -log [OH-]
-Log [ H3O+]+ -Log [OH-] = 14
Scale:
Acid neutral bases
0 7 14
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Indicators ColorsName Acidic Transition Alkaline
1.methyl violet yellow aqua blue
2.methyl yellow red orange yellow
3.bromphenol blue yellow green blue
4.methyl orange red orange yellow
5.methyl red red buff yellow
6.litmus red pink blue
7.bromthymol blue yellow green blue
8.phenol red yellow orange red
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9.phenolphthalein colorless pink red10.thymolphthalein colorless pale bl blue11.alizarin yellow yellow orange red
Transition interval (pH) - above indicators:1. 0.0 -1.6 7. 6.0 - 7.62. 2.9 - 4.0 8. 6.6 - 8.03. 3.0 - 4.6 9. 8.2 - 10.64. 3.2 - 4.4 10. 9.4 - 10.65. 4.8 - 6.0 11. 10.0 - 12.06. 5.5 - 8.0
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Important Indicators:
• Litmus 4. methyl orange
• Phenolphthalein 5. phenol red
• Bromthymol blue 6. universal
Indicator Mechanism: Indicators are weak acids.
In the solution there are nonionized molecules
HIn(red) H+ + In-(blue)
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Choosing Indicators:1. SA-/SB+ BB neutral2. SA-/WB+ MO acidic3. WA-/SB+ phth basic4. WA-/WB+ noneEquivalency point & titration: pH curve slow/
fast/ slow
rapid step [H3O+]=[OH-]
End point and neutralizationA + B S + HOH