Ch. 20 Notes -- Acids and Bases
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Transcript of Ch. 20 Notes -- Acids and Bases
Ch. 20 Notes -- Acids and Bases What makes something an acid?
Acid Properties:
(1) tastes _______-- _______________
(2) corrosive to _________
(3) contains [ ___ ] (or [ _____ ] = “_______________” ions)
(4) proton ([ ___ ]) __________-- Brønsted-Lowry Theory
Example: HCl + H2O ______ + ______
sour lemons
metals
H+ H3O+ hydronium
H+ donor
Cl− H3O+
Properties of BasesWhat make something a base?
Base Properties: (…the opposite of acid properties)
(1) tastes ________ -- ___________ peel , parsley, dark chocolate
(2) feels _____________ -- ________
(3) contains [ _____ ] ions
(4) proton ([H+]) ______________-- Brønsted-Lowry Theory
Example: NH3 + H2O ______ + _______
bitter banana
slippery soap
OH−
acceptor
NH4+ OH−
Content Goal: Students will test pH to determine if household substances are an acid or a base.
Language Goal: Students will show they know the material by filling out the paper that will be
completed in class todaySocial Goal: Students will work together safely
and will follow instructions so that everyone has equal access to lab materials.
pH of food
SafetyNo play fighting or any touching. Move around the room in numerical order.Please keep the beakers on the table. Do
not move the beakers to you, move to the beakers.
Place used test strips into the waste beaker.
Wash your hands after the lab.
Examples of Common Acids:
• Pepsi, _________ juices, ___________, stomach acid, battery acid, _____________, ______
citrus aspirinvinegar DNA
Common Acids
Common Bases• Examples of Common Bases: milk of magnesia, ___________,
drain cleaner, soap, blood, ____________ tablets, ___________ ________.
ammonia
antacid bakingsoda
Indicators• An indicator is a chemical that will change ___________ when
placed in an acidic, basic or neutral environment.
Indicator Colors For Acids
• litmus paper = _______
• phenolphthalein = ___________
• red cabbage juice (universal indicator) = ________
• methyl orange = _______
colors
red
clear
red
red
Indicator Colors for Bases• litmus paper = _______
• methyl orange = ____________
• red cabbage juice (universal indicator) =________
• phenolphthalein = ______
Acid Base
phenolphthalein
blue
yellow
blue
pink
Universal pH Paper : Indicator Colors
Acidic
Basic
Neutral
Acid Vocabulary• strong acid - readily ___________ to produce ______ [H+] ions in
water
Examples: _________, HNO3, _______
• weak acid - produces a __________ amount of [H+] ions when in water
Examples: HC2H3O2 (vinegar) , _________, _________
dissociates many
HCl H2SO4
small
H2CO3 lemon juice
• strong base- readily __________ to produce ______ [OH−] ions in water
Examples: NaOH , ________
• weak base- produces a __________ amount of [OH−] ions when in water
Examples: _____ (ammonia); Mg(OH)2 (milk of magnesia)
Other Vocabulary
• _______________- another term for basic solutions
• _______________- a substance that can act as both an acid and a base
Examples: ___________ , ____________
dissociate many
KOH
small
NH3
Alkaline
Amphoteric
H2O HCO3−
Base Vocabulary
Self-Ionization of Water• Pure water is _____________. It can ionize itself to form OH− and
H3O+ ions in __________ amounts.
H2O + H2O H3O+ + OH−
(or H2O _______ + _______ )
• The universal indicator color is ___________ in neutral solutions.
neutralsmall
H+ OH−
green
self-ionization of water
Measuring the Amount of H+ and OH− Ions in a Solution
• _____ Scale- measures the _____________ of [H+] ions in a solution
• _____ Scale- measures the concentration of [ ____ ] ions in a solution
Formulas
pH = − (log [H+]) pOH = −(log [OH−])
[H+] = 10−pH [OH−] = 10−pOH
[H+] x [OH−] = 1 x 10−14 pH + pOH = 14
• With the pH scale, we have another way to define acids and bases:
Acids have a pH _________7.0
Bases have a pH _________7.0
Neutral pH ___7.0
pH concentration
pOH OH−
below
above
=
pH Testing
Alkalinity Testing
Practice Problems:
1) a) Calculate the pH of a 0.001 M HCl solution
b) What is the pOH of this solution?
c) What is the concentration of [OH−] ions in the solution?
2) a) Calculate the pOH of a NaOH solution that has a pH of 8.50
b) What is the [OH−] of this solution?
c) What is the concentration of [H+] ions in the solution?
[H+] = 0.001 M So…pH = − (log 0.001 M) pH = 3
pH + pOH = 14 So…14 − 3 = pOH pOH = 11
[OH−] = 10−pOH [OH−] = 10−11 Molar or 1 x 10−11 M
So…14 − 8.5 = pOHpH + pOH = 14
[OH−] = 10−5.5 Molar or 3.16 x 10−6 M[OH−] = 10−pOH
[H+] = 10−pH [H+] = 10−8.5 Molar or 3.16 x 10−9 M
pOH = 5.5
Neutralization Reactions
When an acid and base are mixed, the reaction produces _______
and ___________.
• If the initial concentrations and volumes of the reactants are equal, the products will be ____________... (pH= 7.0)
• All neutralization reactions are ___________ replacement reactions.
HX + M(OH) ______ + ______
salt
water
neutral
double
MX H2O(“Salt”)
Titration• Mixing an acid with a base to
determine a __________________ is called “titration.”
• An ____________ is used to determine when neutralization has occurred.
• ________________ Solution - the solution of known concentration
• ______ _________ - the point of neutralization when titrating
• At the ______ point, the moles of [H+] ions = moles of [OH−] ions.
concentration
indicator
Standard
End Point
end
(Macid)x(Vacid) = (Mbase)x(Vbase)
Practice Problems:
(1) A 25 mL solution of HNO3 is neutralized by 18 mL of 1.0 M NaOH standard solution using phenolphthalein as an indicator. What is the concentration of the HNO3 solution?
(2) How many mL of 2.0 M KOH will it take to neutralize 55 mL of a 0.76 M HCl standard solution?
Determining the Concentration of an Acid (or Base) by Titration
( ) x ( ) = ( ) x ( )
( ) x ( ) = ( ) x ( )
Macid 25 mL 1.0 M 18 mL
Macid = 0.72 Molar
0.76 M 55 mL 2.0 M Vbase
Vbase = 20.9 mL