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Acids & BasesAcids & Bases
Learning OutcomesLearning Outcomes
Experiment to classify acids and bases Experiment to classify acids and bases using their characteristic properties. (Ch using their characteristic properties. (Ch 7)7)
• Include: indicators, pH, reactivity with Include: indicators, pH, reactivity with metalsmetals
Learning OutcomesLearning Outcomes
Discuss the occurrence of acids and Discuss the occurrence of acids and bases in biological systems, industrial bases in biological systems, industrial processes, and domestic applications processes, and domestic applications (Ch 8)(Ch 8)
• Include: safety and health considerationsInclude: safety and health considerations
Learning OutcomesLearning Outcomes
Explain how acids and bases interact to Explain how acids and bases interact to form a salt and water in the process of form a salt and water in the process of neutralization. (Ch 7)neutralization. (Ch 7)
Learning OutcomesLearning Outcomes
Describe the formation and Describe the formation and environmental impact of various forms of environmental impact of various forms of pollution. (Ch 8)pollution. (Ch 8)
Examples: acid precipitation, ground-level Examples: acid precipitation, ground-level ozone, air-borne particulates, smog, ozone ozone, air-borne particulates, smog, ozone depletion, respiratory ailments & acidified depletion, respiratory ailments & acidified lakes.lakes.
7.1 Common Acids and Bases7.1 Common Acids and Bases
AcidsAcids
often occur naturallyoften occur naturally
eg) Lactic acid in sore muscles (not eg) Lactic acid in sore muscles (not enough oxygen present during work)enough oxygen present during work)
eg) many fruits including citrus and eg) many fruits including citrus and pineapplepineapple
PropertiesProperties
Taste sourTaste sour– Citric Acid Citric Acid CC66HH88OO77
Feel wateryFeel watery
Caustic (corrosive)Caustic (corrosive)– They burnThey burn
Svante ArrheniusSvante Arrhenius
Found that acids are Found that acids are
ionic compounds and when ionic compounds and when
dissolved (aq) they separate dissolved (aq) they separate
into their ions. into their ions.
He defined acids as substances that He defined acids as substances that
produce hydrogen ions in solution.produce hydrogen ions in solution.
HCl ions separate in water to make H+ HCl ions separate in water to make H+ and Cland Cl--
The more HThe more H++ ions present in solution the ions present in solution the stronger the acidstronger the acid
BasesBases
Often found naturally in foods or Often found naturally in foods or prescription drugs. prescription drugs.
Materials which are bases are Materials which are bases are referred to as being basic or alkaline.referred to as being basic or alkaline.
– Eg) Quinine is a base found in cinchona Eg) Quinine is a base found in cinchona bark and used to make tonic water and bark and used to make tonic water and medicine for malaria.medicine for malaria.
– Eg) bases are used to make soap.Eg) bases are used to make soap.NaOHNaOH
PropertiesProperties
Taste bitterTaste bitter
Feel slipperyFeel slippery
Caustic (corrosive)Caustic (corrosive)– Eat awayEat away– More dangerous than acidsMore dangerous than acids
ArrheniusArrhenius found that bases are ionic found that bases are ionic compounds and when dissolved (aq) compounds and when dissolved (aq) they separate into their ions. He they separate into their ions. He defined bases as substances that defined bases as substances that produce hydroxide ions in solution.produce hydroxide ions in solution.
• NaOH separates in solution to make NaOH separates in solution to make Na+ and OH-Na+ and OH-
• The more OH- ions present in solution The more OH- ions present in solution the stronger the basethe stronger the base
Na(OH) NaNa(OH) Na++ + OH + OH--
NOTE: Ammonia NHNOTE: Ammonia NH33 is a base when is a base when
dissolved in water. Why? dissolved in water. Why?
NHNH33 + H + H22O O NH NH44++ + OH + OH--
The ammonia atom steals one H from The ammonia atom steals one H from water to form OH-water to form OH-
ammonia atom vs. ammonium ionammonia atom vs. ammonium ion
AssignmentAssignment
P 218 1-4 (20), P 218 1-4 (20), BLM 7-5BLM 7-5BLM 7-6BLM 7-6
7.2 pH: A Powerful Scale7.2 pH: A Powerful Scale
IndicatorsIndicators – molecules which change – molecules which change colour with changes in the amount of Hcolour with changes in the amount of H++
(aq) ions or OH(aq) ions or OH--(aq) ions present.(aq) ions present.
Eg) phenolphthaleinEg) phenolphthalein• turns red in base, stays clear in acidic and turns red in base, stays clear in acidic and
neutral conditions.neutral conditions.• CSI use this to determine presence of CSI use this to determine presence of
bloodblood
Eg) Litmus paperEg) Litmus paper• Blue Blue R Reded in Ac in Acidid• Red Red BBlue in lue in BBasease
INDICATORS DO NOT TELL THE INDICATORS DO NOT TELL THE STRENGTH OF THE ACID OR BASE.STRENGTH OF THE ACID OR BASE.
IndicatorIndicator Color in AcidColor in Acid Color in neutral Color in neutral waterwater
Color in BaseColor in Base
Red LitmusRed Litmus No changeNo change No changeNo change BlueBlue
Blue LitmusBlue Litmus RedRed No changeNo change No changeNo change
Phenolphthalein Phenolphthalein
TurmericTurmeric
No changeNo change
YellowYellow
No changeNo change
No changeNo change
RedRed
RedRed
Note: VERY little indicator is needed Note: VERY little indicator is needed in the tests. Too much indicator can in the tests. Too much indicator can change the pH of the acid or base. change the pH of the acid or base.
Example: Phenolphthalein is a weak Example: Phenolphthalein is a weak acid.acid.
The pH ScaleThe pH Scale
pH pH – stands for “power of the – stands for “power of the hydrogen ion”hydrogen ion”a scale used to measure the strength a scale used to measure the strength of an acid or base.of an acid or base.Is measured with an electronic pH Is measured with an electronic pH meter OR by looking at the colours on meter OR by looking at the colours on Universal indicator paper.Universal indicator paper.Note: neutral solutions have equal Note: neutral solutions have equal numbers of H+ and OH- ions.numbers of H+ and OH- ions.
HH22O O H H++ + OH + OH--
so pure water is neutral.so pure water is neutral.
Strongest Acid
Neutral
Strongest Base
• Each change in 1 pH changes the Each change in 1 pH changes the strength by a factor of 10.strength by a factor of 10.
• Eg) pH 1 is 10Eg) pH 1 is 1033 or 1000 times as strong or 1000 times as strong an acid as pH 4.an acid as pH 4.
AssignmentAssignment-P 225 1-5 (21), BLM 7-7 & 7-8-P 225 1-5 (21), BLM 7-7 & 7-8-Fill out chart of important acids-Fill out chart of important acidsand bases in notesand bases in notes
BLM 7-8BLM 7-8
1.1. BaseBase
2.2. AcidAcid
3.3. NeitherNeither
4.4. NeitherNeither
5.5. Base Base
6.6. AcidAcid
7.7. AcidAcid
8.8. BaseBase
9.9. NeitherNeither
10.10. AcidAcid
11.11. AcidAcid
12.12. AcidAcid
http://www.lab-initio.com/sci_chemistry.html
7.3 Properties of Acids and Bases7.3 Properties of Acids and Bases
The strength of an acid is determined byThe strength of an acid is determined by
2 factors:2 factors:
ConcentrationConcentration – how much acid is – how much acid is dissolved in water.dissolved in water.
Percent IonizationPercent Ionization – the number of – the number of molecules that will ionize to release H+ molecules that will ionize to release H+ ions for every 100 molecules dissolved.ions for every 100 molecules dissolved.
ConcentrationConcentration Percent Percent IonizationIonization
Concentrated Dilute H2CO3 2H+ + CO32-
99mL HCl 1mL HCL 200 1 Weak1mL H2O 99mL H2O
H2SO4 2H+ + SO42-
None all Strong
Note: For Percent Ionization the # of H+ Note: For Percent Ionization the # of H+ ions in the acid DOES NOT DETERMINE ions in the acid DOES NOT DETERMINE THE STRENGTH OF THE ACIDTHE STRENGTH OF THE ACID
The strength is only determined by the The strength is only determined by the amount of H+ ions that go into solutionamount of H+ ions that go into solution
Not all acids release H+ ions equally Not all acids release H+ ions equally easily. (Generally the more polar the easily. (Generally the more polar the bond the stronger the acid.)bond the stronger the acid.)
Eg) CHEg) CH33COOH has 4 H atoms but COOH has 4 H atoms but
only 1 ionizes:only 1 ionizes:
CHCH33COOH COOH CH CH33COOCOO-- + H + H++
Acetic acidAcetic acid
Copy the charts for common acids Copy the charts for common acids and bases on p 227.and bases on p 227.
Why is ammonia considered a base Why is ammonia considered a base when dissolved in water? HINT: when dissolved in water? HINT: Guess the products of NHGuess the products of NH33 + H + H22OO
NHNH33 + H + H22O = NHO = NH44++ + OH + OH--
AssignmentAssignment
P 230 1-5 P 230 1-5
BLM 7-12, 7-13 & 7-14BLM 7-12, 7-13 & 7-14
7.4 Neutralization Reactions7.4 Neutralization Reactions
Acids and Bases react with each other to Acids and Bases react with each other to form a salt and water.form a salt and water.
Eg) HCl + NaOH Eg) HCl + NaOH NaCl + H NaCl + H22OO
double displacementdouble displacement
Complete and balance the reactions, name Complete and balance the reactions, name the salts.the salts.
1H1H22SOSO44 + 2KOH + 2KOH
1H1H22SO4 + 2NaOH SO4 + 2NaOH
2HNO2HNO33 + 1Ca(OH) + 1Ca(OH)22
HH22COCO33 + Mg(OH) + Mg(OH)22
2H2H22O + KO + K22(SO(SO44))
Salt: Salt: Potassium SulfatePotassium Sulfate
2H2H22O + 1NaO + 1Na22SOSO44
Salt: Salt: Sodium SulfateSodium Sulfate
2H2H22O + 1Ca(NO3)O + 1Ca(NO3)22
Salt: Salt: Calcium NitrateCalcium Nitrate
2H2H22O + MgCOO + MgCO33
Salt: Salt: Magnesium Magnesium CarbonateCarbonate
Making AcidsMaking Acids
OxidesOxides – compounds containing one – compounds containing one element with oxygen.element with oxygen.
Eg) CO, COEg) CO, CO22, Al, Al22OO33, SO, SO33, NO, NO22
Non-metal oxidesNon-metal oxides – compounds – compounds containing a single non-metal combined containing a single non-metal combined with oxygen.with oxygen.
ALL non-metal oxides react with water ALL non-metal oxides react with water to form acids.to form acids.
Eg) COEg) CO22 + H + H22O O H H22COCO33
carbonic acid (makes rain slightly carbonic acid (makes rain slightly acidic)acidic)
Eg) SOEg) SO33 + H + H22O O H H22SOSO4 4 sulfuric sulfuric
acidacid
AssignmentAssignment
P 236 1-5 P 236 1-5
BLM 7-16, 7-17, 7-19 BLM 7-16, 7-17, 7-19
Review P 238-239 1-17, 20, & 21Review P 238-239 1-17, 20, & 21
