1 The Chemistry of Acids and Bases. 2 3 Acid and Bases.
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Transcript of 1 The Chemistry of Acids and Bases. 2 3 Acid and Bases.
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The Chemistry of The Chemistry of Acids and BasesAcids and Bases
The Chemistry of The Chemistry of Acids and BasesAcids and Bases
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Acid and BasesAcid and Bases
VinegarVinegarAcetic AcidOr
Vinegar
Acetic AcidOr
Vinegar
Vinegar is a weak acidthat has many household uses
Vinegar is a weak acidthat has many household uses
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Some Properties of Acids
Produce H3O+ ions in water (the hydronium ion is a hydrogen ion
attached to a water molecule)
Taste sour
Reacts with a metal to produce hydrogen gas
Electrolytes
React with bases to form a salt and water
pH is less than 7
Turns blue litmus paper to red “Blue to Red A-CID”
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Anion Ending Acid Name
-ide hydro-(stem)-ic acid
-ate (stem)-ic acid
-ite (stem)-ous acid
Acid Nomenclature Review
Binary Binary
Ternary Ternary
An easy way to remember which goes with which…An easy way to remember which goes with which…
““In the cafeteria, youIn the cafeteria, you ATEATE somethingsomething ICICky”ky”
1212Acid Nomenclature Flowchart
h yd ro - p re fix-ic en d in g
2 e lem en ts
-a te en d in gb ecom es-ic en d in g
-ite en d in gb ecom es
-o u s en d in g
n o h yd ro - p re fix
3 e lem en ts
AC ID Ss ta rt w ith 'H '
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• HBr HBr (aq)(aq)
• HH22COCO33
• HH22SOSO33
hydrohydrobromicbromic acidacid
carboncarbonicic acidacid
sulfursulfurousous acidacid
Acid Nomenclature Review
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Name ‘Em!
HCl (aq)HCl (aq)
HI (aq)HI (aq)
H2SO4 (aq)H2SO4 (aq)
HNO2 (aq) HNO2 (aq)
HIO3 (aq) HIO3 (aq)
HydroHydrochlorchloricic acid acid HydroHydrochlorchloricic acid acid
HydroHydroiodiodicic acid acid HydroHydroiodiodicic acid acid
SulfurSulfuricic acid acid SulfurSulfuricic acid acid
NitrNitrousous acid acid NitrNitrousous acid acid
IodIodicic acid acid IodIodicic acid acid
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Some Properties of Bases
Produce OHProduce OH-- ions in water ions in water
Taste bitter, chalkyTaste bitter, chalky
Are electrolytesAre electrolytes
Feel soapy, slipperyFeel soapy, slippery
React with acids to form salts and waterReact with acids to form salts and water
pH greater than 7pH greater than 7
Turns red litmus paper to blue “Turns red litmus paper to blue “BBasic asic BBlue”lue”
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Some Common Bases
NaOHNaOH sodium hydroxidesodium hydroxide lyelye
KOHKOH potassium hydroxidepotassium hydroxide liquid soapliquid soap
Ba(OH)Ba(OH)22 barium hydroxidebarium hydroxide stabilizer for plasticsstabilizer for plastics
Mg(OH)Mg(OH)22 magnesium hydroxidemagnesium hydroxide “MOM” Milk of magnesia“MOM” Milk of magnesia
Al(OH)Al(OH)33 aluminum hydroxidealuminum hydroxide Maalox (antacid)Maalox (antacid)
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Acid/Base definitions
• Definition #1: Arrhenius (traditional)
Acids – produce H+ ions which produce hydronium ion (H3O+) when dissolved in water.
Bases – produce OH- ions
(problem: some bases don’t have hydroxide ions!)
2121Arrhenius acid is a substance that produces H+ (H3O+) in water
Arrhenius base is a substance that produces OH- in water
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Acid/Base Definitions
• Definition #2: Brønsted – Lowry
Acids – proton donor
Bases – proton acceptor
A “proton” is really just a hydrogen atom that has lost it’s electron!
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A Brønsted-Lowry acid is a proton donorA Brønsted-Lowry base is a proton acceptor
acidacidbasebaseAccepts a Proton or H+
Accepts a Proton or H+
Donates a Proton or H+
Donates a Proton or H+
2525Acids & Base Acids & Base DefinitionsDefinitions
Lewis acid - a Lewis acid - a substance that substance that accepts an electron accepts an electron pairpair
Lewis base - a Lewis base - a substance that substance that donates an electron donates an electron pairpair
Definition #3 – Lewis Definition #3 – Lewis
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The The pH scalepH scale is a way of is a way of expressing the strength of expressing the strength of acids and bases.acids and bases.
The The pH scalepH scale is a way of is a way of expressing the strength of expressing the strength of acids and bases.acids and bases.
Instead of using very small Instead of using very small numbers, we just use the numbers, we just use the NEGATIVE power of 10 on the NEGATIVE power of 10 on the Molarity of the HMolarity of the H33OO++ (or OH (or OH--) )
ion.ion.
Instead of using very small Instead of using very small numbers, we just use the numbers, we just use the NEGATIVE power of 10 on the NEGATIVE power of 10 on the Molarity of the HMolarity of the H33OO++ (or OH (or OH--) )
ion.ion.
pH under 7 = acidpH 7 = neutralpH over 7 = base
pH under 7 = acidpH 7 = neutralpH over 7 = base
3232Calculating the pH
pH = - log [H3O+](Remember that the [ ] mean Molarity)
Example: If [H3O+] = 1 X 10-10
pH = - log 1 X 10-10
pH = - (- 10)
pH = 10
Example: If [H3O+] = 1.8 X 10-5
pH = - log 1.8 X 10-5
pH = - (- 4.74)
pH = 4.7
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Try These!Try These!
Find the pH of these:Find the pH of these:
1)1) A 0.15 M solution of Hydrochloric acidA 0.15 M solution of Hydrochloric acid
Answer: pH = .82 Answer: pH = .82
2) A 3.00 X 102) A 3.00 X 10-7-7 M solution of Nitric acid M solution of Nitric acid
Answer: pH = 6.52Answer: pH = 6.52
3434pH calculations – Solving for pH calculations – Solving for HH33O+O+pH calculations – Solving for pH calculations – Solving for HH33O+O+
If the pH of Coke is 3.12, If the pH of Coke is 3.12,
what is the [Hwhat is the [H33OO++]?]?
Because pH = - log [HBecause pH = - log [H33OO++] then ] then
- pH = log [H- pH = log [H33OO++]]
Take antilog (10Take antilog (10xx) of both sides ) of both sides
*** to find antilog on your calculator, *** to find antilog on your calculator,
look for “Shift” or “2look for “Shift” or “2nd nd function” and then the log buttonfunction” and then the log button
[H[H33OO++] =] = 1010-pH-pH
[H[H33OO++] = 10] = 10-3.12-3.12 = 7.59 x 10 = 7.59 x 10-4-4 M M
(On your calculator: 2(On your calculator: 2ndnd, log, -3.12, enter), log, -3.12, enter)
3535You try thisYou try this
• A solution has a pH of 8.5. What is the A solution has a pH of 8.5. What is the molarity of hydronium (Hmolarity of hydronium (H33OO++) ions in ) ions in the solution?the solution?
- log [H- log [H33OO++] = pH ] = pH
- log [H- log [H33OO++] = 8.5] = 8.5
log [Hlog [H33OO++] = - 8.5] = - 8.5
antilog (log [H3O+]) = antilog (log [H3O+]) = Antilog -8.5Antilog -8.5
[H[H33OO++] = 10] = 10-8.5-8.5
[H[H33OO++] = 3.2 X 10] = 3.2 X 10-9 -9 MM
- log [H- log [H33OO++] = pH ] = pH
- log [H- log [H33OO++] = 8.5] = 8.5
log [Hlog [H33OO++] = - 8.5] = - 8.5
antilog (log [H3O+]) = antilog (log [H3O+]) = Antilog -8.5Antilog -8.5
[H[H33OO++] = 10] = 10-8.5-8.5
[H[H33OO++] = 3.2 X 10] = 3.2 X 10-9 -9 MM
3636pOH
• Since acids and bases are Since acids and bases are opposites, pH and pOH are opposites, pH and pOH are opposites!opposites!
• pOH does not really exist, but it is pOH does not really exist, but it is useful for changing bases to pH.useful for changing bases to pH.
• pOH looks at the perspective of a pOH looks at the perspective of a basebase
pOH = - log [OHpOH = - log [OH--]]Since pH and pOH are on opposite Since pH and pOH are on opposite
ends,ends,pH + pOH = 14pH + pOH = 14
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[H[H33OO++], [OH], [OH--] and pH] and pH
What is the pH of a 0.0010 M What is the pH of a 0.0010 M NaOHNaOH solution? solution?
pOH = - log 0.0010pOH = - log 0.0010
pOH = 3pOH = 3
pH = 14 – 3 = 11pH = 14 – 3 = 11
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H2SO4, HNO3, HCl, HBr, HI, and HClO4 are among the only known strong acids.
Strong and Weak AcidsStrong and Weak Acids
The strength of an acid is determined by the amount of IONIZATION or DISSOCIATION when put in water.
The strength of an acid is determined by the amount of IONIZATION or DISSOCIATION when put in water.
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The strength of an base is determined by the amount of IONIZATION or DISSOCIATION when put in water.
• NaOH (aq) ---> NaNaOH (aq) ---> Na+ + (aq) + OH(aq) + OH- - (aq)(aq)
Strong and Weak BasesStrong and Weak Bases
Strong bases include Strong bases include KOH, NaOH, RbOH, KOH, NaOH, RbOH, CsOH, Ca(OH)CsOH, Ca(OH)22, Sr(OH), Sr(OH)22, ,
and Ba(OH)and Ba(OH)22
4444Finding the pH
Paper testsPaper tests
Litmus paperLitmus paper
Blue to red is “a-cid”Blue to red is “a-cid”
Red to blue is base Red to blue is base
pH paperpH paper
Turns various colorsTurns various colors
according to the pHaccording to the pH
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Finding the pHpH MeterpH MeterTests the voltage of the Tests the voltage of the
electrolyteelectrolyte
Converts the voltage to pHConverts the voltage to pH Very cheap, accurateVery cheap, accurate
Must be calibrated with a Must be calibrated with a buffer solutionbuffer solution
4646pH indicators
• Indicators are dyes that can be added that will change color in the presence of an acid or base.
• Some indicators only work in a specific range of pH
• Once the drops are added, the sample is ruined
• Some dyes are natural, like radish skin or red cabbage
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TitrationTitrationTitrationTitration
1. Add solution from the buret.1. Add solution from the buret.2. Reagent (base) reacts with 2. Reagent (base) reacts with
compound (acid) in solution compound (acid) in solution in the flask.in the flask.
3.3. Indicator shows when exact Indicator shows when exact neutralization reaction has neutralization reaction has occurred. (Acid = Base)occurred. (Acid = Base)
This is called This is called NEUTRALIZATION.NEUTRALIZATION.