Transcript Solutions Acids Bases Notes solutions_acids__bases

Solubility
Chart
At higher
temperatures:
•Most solids
become more
soluble
•Most gases
become less
soluble.
Therefore…
Solids tend to dissolve best when:
o Heated
o Stirred
o Ground into small particles
Liquids tend to dissolve best
when:
o The solution is cold
o Pressure is high
“Like Dissolves Like”
Nonpolar solutes dissolve best in nonpolar
solvents
Fats
Steroids
Waxes
Benzene
Hexane
Toluene
Polar and ionic solutes dissolve best in polar
solvents
Inorganic Salts
Sugars
Water
Small alcohols
Acetic acid
Saturation of Solutions
 A solution that contains the maximum
amount of solute that may be dissolved
under existing conditions is saturated.
 A solution that contains less solute than
a saturated solution under existing
conditions is unsaturated.
 A solution that contains more dissolved
solute than a saturated solution under
the same conditions is supersaturated.
 http://www.youtube.com/watch?v=tkH
Q2e6BYbI
Ionic Solutions
Ionic Compounds in Water
Dissociation – the separation of ions that
occur when an ionic compound dissolves.
NaCl
(aq)
→
Na1+ + Cl1PHET Simulation
http://phet.colorado.edu/en/simulation/soluble-salts
http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/molvie1.swf
Dissociation
Example: dissociation of sodium
chloride
H2O
NaCl (s) → Na
1+ (aq)
+ Cl
1-(aq)
Example: dissociation of calcium
chloride
H2 O
CaCl2
(s)
→ Ca
2+ (aq)
+ 2 Cl
1-(aq)
Concentration of Solutions
Vocabulary
Solution:
A liquid (usually) with something dissolved inside.
Solute:
A substance dissolved in a solvent liquid. (lesser
ingredient)
Solvent:
The liquid that dissolves or holds the solute.
(greater ingredient)
Concentration:
The strength of the solution measured as the ratio
of the amount of solute vs amount of solvent
(%, mg/L, mmol/L)
Molarity
Molarity is the ratio of moles of solute
to liters of solution (mostly solvent).
M = mol/L
*Mole Chart 3
Demo – Mixing a solution of KMnO4
Solving M = mol/L with algebra for:
Moles: mol = L* M
Liters: L = mol/M
Grams: L* M = mol x mw = g
÷x
Mole Chart (3)
Volume of
Gas at STP
(L)
Mass (g)
MW
X
÷
Moles
÷ x
A#
Solution
Concentration
(M)
22.4L
6.02x1023
Particles
(atoms or
Molecules)
Dilutions
Demo: Dilute KMnO4 solution from Molarity
Demo. Calculate new concentration.
1. C1V1=C2V2
2. C – concentration, V - volume
3. The concentration decreases
proportionally to the increase in volume.
4. C1v1 = c2V2
5. V2 = v1 + H2O = Total Final Volume
Asmt: 15-2 all, Get a head start on Beer’s
Law Lab
Acids & Bases
pH Balance?
Acid – Base Vocabulary
Acid
Base
Indicator
Neutralization
Hydronium ion
Amphoteric
Conjugate acid
Conjugate base
Dissociation
pH
Buffer
Titration
Equivalence point
Video: Elements of Chemistry Acids, Bases & Salts
Household Acids & Bases Lab
Solution
Vinegar
Ammonia
Lemon juice
Soft drink
Drain
cleaner
Detergent
Baking soda
Prune Juice
Berry Juice
Blue litmus
Red litmus
Universal
Indicator
pH
Mentos & Pop
http://www.stevespanglerscience.co
m/experiment/00000109
Properties of Acids vs Bases
Acids:
Taste Sour – vinegar!
Feel like water but sting
cuts.
Turn litmus red.
Have pH lower than 7
React with active metals
to form explosive H2
gas.
Act as electrolytes to
conduct electricity.
Neutralize bases!
Bases:
Taste bitter – soap!
Feel slippery.
Turn litmus blue.
Have pH higher than 7
Don’t react with most
metals.
Act as electrolytes to
conduct electricity.
Neutralize acids!
Acids React with Active
Metals
Acids react with active metals to form
salts and hydrogen gas.
Mg + 2HCl  MgCl2 + H2(g)
Acids React with Carbonates
2HC2H3O2 + Na2CO3
2 NaC2H3O2 + H2O + CO2
Products of Neutralization
HCl + NaOH 
NaCl + H2O
H2SO4 + Ca(OH)2  CaSO4 + 2 H2O
HNO3 + KOH  KNO3 + H2O
The products of neutralization are always
salt and _______.
water
a ______
Acids Neutralize Bases
HCl + NaOH  NaCl + H2O
Neutralization reactions ALWAYS
produce a salt and water.
Effects of Acid Rain on Marble
(calcium carbonate)
George Washington:
BEFORE
George Washington:
AFTER
Examples of Bases
 Sodium hydroxide
(lye), NaOH
 Potassium hydroxide,
KOH
 Magnesium hydroxide,
Mg(OH)2
 Calcium hydroxide
(lime), Ca(OH)2
Bases Effect Indicators
Red litmus paper turns blue
in contact with a base.
Phenolphthalein
turns purple in a
base.
Bases
have a pH
greater
than 7
Bases Neutralize
Acids
Milk of Magnesia contains
magnesium hydroxide, Mg(OH)2,
which neutralizes stomach acid,
HCl.
2 HCl + Mg(OH)2
MgCl2 + 2 H2O
Acids you must know:
Strong Acids
Weak Acids
Sulfuric acid, H2SO4
Phosphoric acid, H3PO4
Hydrochloric acid, HCl
Acetic acid, HC2H3O2
Nitric acid, HNO3
Carbonic acid, H2CO3
Naming Acids – Correspond to
Anion Suffices
A. -ide ion
Ex: chloride, ClB. -ite ion
Ex: sulfite, SO3-2
C. –ate ion
Ex: phosphate, PO4-3
A. Hydro___ic acid
Ex: Hydrochloric acid,
HCl
B. –ous acid
Ex: sulfous acid,
H2SO3
C. –ic acid
Ex: phosphoric acid,
H3PO4
Write the Names & Formulas of
the following Acids
1.
2.
3.
4.
5.
6.
7.
8.
HF
H3PO3
H2SO4
HCl
HClO3
HI
HNO2
HC2H3O2
1.
2.
3.
4.
5.
6.
7.
8.
hydrobromic acid
nitric acid
hydrosulfuric acid
hydrocyanic acid
sulfurous acid
boric acid
chlorous acid
carbonic acid
Sulfuric Acid
 Highest volume production
of any chemical in the U.S.
 Used in the production of
paper
 Used in production of
fertilizers
 Used in petroleum refining
Nitric Acid
Used in the production
of fertilizers
Used in the production
of explosives
Nitric acid is a volatile
acid – its reactive
components evaporate
easily
Stains proteins
(including skin!)
Hydrochloric Acid
Used in the pickling
of steel
Used to purify
magnesium from sea
water
Part of gastric juice,
it aids in the
digestion of protein
Sold commercially as
“Muriatic acid”
Phosphoric Acid
o A flavoring agent in
sodas
o Used in the
manufacture of
detergents
o Used in the
manufacture of
fertilizers
o Not a common
laboratory reagent
Acetic Acid
Used in the
manufacture of
plastics
Used in making
pharmaceuticals
Acetic acid is the acid
present in vinegar
Carbonic Acid
•Removes
carbon dioxide
from the body.
•Mediates the
carbon dioxide
levels in the
atmosphere.
Arrhenius Acids & Bases
Acids:
Release H+ ions by
dissociation.
Example: HCl
Combine H+ with
any negative ion
on your ion chart
to form an acid.
Examples: ???
Bases:
Release OH- ions
by dissociation.
Example: NaOH
Combine OH- with
any metal on the
periodic table to
form a base.
Examples: ???
Arrhenius Definition
An acid is a substance that dissociates
in water to produce hydrogen ions.
HCl(l) + H2O (l) → H1+ (aq) + Cl1- (aq)
H2SO4 (l) + H2O (l) ↔ H1+ (aq) + HSO41-(aq)
- Must be dissolved in water.
- Does not explain why the covalent
bonds are broken.
Arrhenius Definition
An base is a substance that dissociates in
water to produce hydroxide ions (OH1-).
NaOH → Na1+ (aq) + OH1- (aq)
Ba(OH)2 ↔ Ba2+ (aq) + 2 OH1- (aq)
Does not explain compounds with
characteristics of bases – NH3
Arrhenius Explanations
H+ provides the sour taste & stings.
OH- the bitter taste & is slippery.
Dissociation of both acids & bases
produces dissolved ions which act as
electrolytes.
Neutralization occurs when H+ & OHcombine to form H2O. The left overs
produce a salt like NaCl.
Bronsted-Lowry Acids & Bases
Acids:
Donate H+ ions.
Example: Acetic
acid & amino acids.
H+ ions are
protons.
Bases:
Accept H+ ions.
Example:
Ammonia, NH3
All inclusive
including bases
ignored by
Arrhenius.
Acids are Proton Donors
Monoprotic acids
Diprotic acids
HCl
H2SO4
HC2H3O2
H2CO3
HNO3
Triprotic acids
H3PO4
Bronsted-Lowry Definition
An acid is any substance that can
donate H+ ions.
HCl(g) + H2O (l) → H1+ (aq) + Cl1- (aq)
A base is any substance that can accept
H+ ions.
NH3 (g) + H2O
(l)
→ NH4+
(aq)
+ OH1- (aq)
Acid/Base Definitions
 Arrhenius Model
 Acids produce hydrogen ions in
aqueous solutions
 Bases produce hydroxide ions in
aqueous solutions
 Bronsted-Lowry Model
 Acids are proton donors
 Bases are proton acceptors
 Lewis Acid Model
 Acids are electron pair acceptors
 Bases are electron pair donors
Conjugate Acids & Bases
Acids release H+ & bases accept H+.
Once an acid releases its H+ it
becomes a base that can accept H+
& vice versa.
Examples:
H2CO3 vs HCO3-1
NH3 vs NH4+1
H2O vs H3O+1
Conjugate acid-base pairs
The acid that loses a H+ ion becomes the
conjugate base. The base that gains
the H+ ion becomes the conjugate acid.
HCl(g) + H2O (l) → H3O1+ (aq) + Cl1- (aq)
acid
base
NH3 (g) + H2O
base
acid
conj
(l)
acid
→ NH4+
conj
acid
conj
(aq)
base
+ OH1- (aq)
conj
base
Hydronium Ion
Water is amphoteric – it can act as both
an acid & a base.
When water acts as a base, it forms the
hydronium ion.
H2O + H+  H3O+
H+ ions always bind to something.
When water acts as an acid it forms OH-.
H20  OH- + H+
The fraction of water that normally
dissociates is 10-7 M. A very small
fraction! 1/10million!
Water
Water as a molecule is
unique because it is
amphoteric. This means
that it can react as either
an acid or a base.
H2O + H2O

H3O+ + OH-
Ionization of HCl and formation of
hydronium ion, H3O+
H2 O +
Proton
acceptor
HCl
Proton
donor

H3O+ + Cl-
Hydrogen ions are “protons”
Proton exchange animation
http://web.jjay.cuny.edu/~acarpi/NS
C/7-ph.htm
Acid Base Simulation (pHET)
http://phet.colorado.edu/en/simulatio
n/acid-base-solutions
Acids Effect Indicators
Blue litmus paper turns red in contact
with an acid.
Acids
Have a
pH less
than 7
pH Measures the H+ Concentration
pH uses logs which are just powers of
10.
pH measures the electric “potential” of
H+ ions in a solution.
pH is calculated as the negative “power”
of 10 of the H+ ion concentration.
The equation for pH is pH = -log[H+]
[brackets] mean concentration in
Molarity.
pH 7 is neutral, above 7 is basic & below
7 is acidic.
Simple pH Calculations
H+ Molarity
pH
.001
Power of
10
10-3
3
Acid or
Base?
Acid
.00001
10-5
5
Acid
.0000001
10-7
7
neutral
.000000001
10-9
9
Base
.0000000000
01
.00047
10-12
12
Base
10-3.3
3.3
Acid
[H+], [OH-], pH, pOH
H2O  H+ + OHThis reaction goes back & forth in a
balanced equilibrium quantified as:
[H+][OH-] = 10-14
When neutral each are equal:
[H+] = 10-7M = [OH-]
pH =7, pOH =7
In general pH + pOH =14
pH = -log[H+], pOH = -log[OH-]
pH and pOH Calculations
+
H
[OH-] = 1 x 10-14
[H+]
-
OH
pH
pOH = 14 - pH
pH = 14 - pOH
pOH = -log[OH-]
[OH-] = 10-pOH
pH = -log[H+]
[H+] = 10-pH
[H+] = 1 x 10-14
[OH-]
pOH
pH Homework
http://www.sciencegeek.net/Chemist
ry/taters/Unit8pH.htm
Write down questions as knowns &
unknowns, show work and answers
for questions 1-22
pH = -log [H3O+]
pOH = -log [OH1-]
1.Calculate the pOH of a solution
whose
[OH1-] = 5.5 x 10-5 M.
2.Calculate the pH of a solution whose
[H3O+] = 9.87 x 10-7 M.
3.Calculate the pOH of a solution
whose
[OH1-] = 9.5 x 10-2 M.
4.Calculate the pH of a solution whose
[H3O+] = 6.7 x 10-13 M.
[H3O+] = 10-pH
[OH1-] = 10-pOH
1.Calculate the
pOH = 8.9.
2.Calculate the
pH = 12.7.
3.Calculate the
pH = 3.2.
4.Calculate the
pH = 7.8.
5.Calculate the
pOH = 4.78.
[OH1-] of a solutions whose
[H3O+] of a solution whose
[H3O+] of a solution whose
[OH1-] of a solution whose
[H3O+] of a solution whose
pH and pOH using
compounds
1.Determine the pH of a 0.0034 M
HNO3 solution.
2.Determine the pOH of a 4.3 x 10-4
M NaOH solution.
3.Determine the pOH of a 0.0034 M
HNO3 solution.
4.Determine the pH of a 4.5 x 10-11
M NaOH solution.
Chemistry
Chapter
16
Acid-Base
Titration
and pH
Self-Ionization of Water
H2O + H2O

H3O+ + OH-
Ion Concentration in Water
Kw – Ionization Constant for
Water
In pure water at 25 C:
[H3O+] = 1 x 10-7 mol/L
[OH-] = 1 x 10-7 mol/L
Kw is a constant at 25 C:
Kw = [H3O+][OH-]
Kw = (1 x 10-7)(1 x 10-7) = 1 x 10-14
H+, OH-, and pH
pH
Scal
e
Calculating pH, pOH
pH = -log10(H3O+)
pOH = -log10(OH-)
Relationship between pH and pOH
pH + pOH = 14
Finding [H3O+], [OH-] from pH, pOH
[H3O+] = 10-pH
[OH-] = 10-pOH
pH
+
pOH
=
14
Measuring pH with wide-range
paper
pH
Indicator
s
and their
ranges
pH Calculations
http://proton.csudh.edu/lecture_help
/phcalcs.html
ACID-BASE REACTIONS
Titrations
H2C2O4 (aq)
acid
H2O(liq)
+
2 NaOH (aq) --->
base
Na2C2O4(aq) + 2
Oxalic acid,
Carry out this reaction using
H2C2O4 a
TITRATION.
Setup for titrating an acid with a base
Titration Curves
Titration
1. Add solution from the
buret.
2. Reagent (base) reacts
with compound (acid)
in solution in the flask.
3. Indicator shows when
exact stoichiometric
reaction has occurred.
(Acid = Base)
This is called
NEUTRALIZATION.
Titrations Problems
Remember: acid = Base
(Vbase)(Mbase) = (Vacid)(Macid)
35.62 mL of NaOH is
neutralized with 25.2 mL of
0.0998 M HCl by titration to an
equivalence point. What is the
concentration of the NaOH?
Titration Calculations
Strong Acids vs. Weak Acids
Strong acids are assumed to be 100%
ionized in solution (good proton donors).
HCl
H2SO4
HNO3
Weak acids are usually less than 5%
ionized in solution (poor proton donors).
H3PO4
HC2H3O2
Organic acids
Organic Acids
Organic acids all contain the “carboxyl” group,
sometimes several of them.
The carboxyl group is a poor proton donor,
so ALL organic acids are weak acids.
Examples of Organic Acids
 Citric acid in citrus fruit
 Malic acid in sour apples
 Deoxyribonucleic acid, DNA
 Amino acids, the building blocks
of protein
 Lactic acid in sour milk and sore
muscles
 Butyric acid in rancid butter
pH Quiz – Determine the pH of:
1. A 4.63 x 10-8M solution of HNO3.
2. A 250L solution containing 4.3mol
of HCl.
3. A 750.0ml solution containing
0.0046mol of NaOH.
4. A 8.9L solution of 0.65mol of
H2SO4.
Titrations
Titrations measure the concentration of
solutions by finding out the amount of a
known solution needed to neutralize an
unknown solution.
Neutralization occurs when Mol H+ = Mol of
OHM = mol/L
mol = L x M
mol = M x V
MaVa = MbVb (a is for acid, b is for base)
Some acids are diprotic or triprotic, some
bases are multi-hydroxy.
AMaVa = BMbVb
(A is for # of H+, B is for # of OH-)
Friday 6-11-04
Prep:
1. Litmus papers, droppers fill up bottles.
2. Graduation Rehearsal
Class
1. End of Year Schedule
2. Vocabulary Assignment
3. Lab – pH of Household Substances
–
–
–
Predictions
Handling the pH probe & storage bottle
Litmus tests & universal indicator
Equilibrium of Reversible Reactions
Many reactions may proceed in both the
forward & backward directions.
Carbonated Water:
CO2(g) + H2O (l)  H2CO3(aq)
Carbonate pop by adding CO2(g) pressure.
CO2(g) + H2O (l)  H2CO3(aq)
Pop goes flat when container is opened!
CO2(g) + H2O (l)  H2CO3(aq)
Example 2: pH of Pop
1) CO2(g) + H2O
(l)
 H2CO3(aq)
2) H2CO3(aq)  H+(aq) + HCO3-(aq)
What is the pH of pop?
When it goes flat, what happens to the
pH?
Strong Acid Dissociation
Weak Acid Dissociation
Equilibrium Ratios
xA(aq) + yB(aq)

zC(aq)
Equilibrium Ratio (K) = products/reactants
Keq = [C]z / [A]x[B]y
Coefficients = exponents!
Carbonated Water Equilibrium Ratio?
Each reaction has a different equilibrium
ratio value.
Large ratios favor the _________, while
small ratios favor the _________.
pH of Household Substances
1.
2.
3.
4.
5.
Make the following data table in your notebook.
Rank & predict pH of samples to be used: soda pop,
drain cleaner, vinegar, ammonia, lemon juice,
detergent, baking soda
½ fill a well in the plate for each sample.
Test with red litmus, blue litmus & then add 1 drop of
universal indicator to observe the color. Dispose
down sink.
pH Probe:
–
–
–
–
–
–
Cap stays on probe. Place storage bottle by faucet.
Rinse probe with distilled water before each test.
Place probe in each sample bottle.
Swirl sample around probe for 30 seconds.
Record pH from top right corner of calculator.
Recap all bottles when not in use.
Titrations Quiz
1. If 20.00ml of acidic drain cleaner is
titrated completely by 18.02ml of
0.100M NaOH, what is the acid’s
concentration?
2. A 25.1ml volume of KOH is titrated
with 43.2ml of 0.150M H2SO4.
What is the molarity of the KOH?
3. A volume of 34.0ml of 0.100M
H3PO4 neutralizes 25.0ml of
Ba(OH)2. What is the concentration
of the barium hydroxide?
Vinegar Titration Lab
Add 10.0 ml of vinegar to the beaker.
Add 4 drops of indicator B, phenolpthalein.
Fill the buret with 1.00M NaOH. Record
the starting volume.
Titrate until the mixture turns pink & stays
pink. Use the minimum of drops.
Measure the final volume and determine
the change in volume of the base.
Use AMaVa = BMbVb to determine the
molarity of the vinegar, HC2H3O2.
Conjugate Acids & Bases
Any acid that can release H+ can re-accept and
bind it to varying degrees.
Strong acids like HCl release essentially all H+
ions. HCl  H+ + ClWeak acids like in vinegar release a small
percentage of H+ ions. Most remain bound.
HC2H3O2  H+ + C2H3O2Salts contain positive & negative ions.
Any negative ion has some capacity to bind with
H+ ions to act like a base. Examples: ???
Conjugates represent examples with or without
H+ attached. Examples: ???