Acid Base Chemistry
Spring 2015
Agenda 5/12/15
• Go Over Tests
▫ Retakes
• Intro to Acid-Base Chemistry
• Red Cabbage Lab
• Notes: Acids and Bases
Acids
What is an acid?
– Compounds that produce H+ ions when dissolved in
aqueous solution
• Arrhenius Model Acid (Original Definition)
Example: HCl(aq) + H20 → H+ (aq)+ Cl-(aq)
• Classified by number of H+ ions that are able to be
produced
• Monoprotic– 1 H+
• Diprotic– 2 H+
Example: H2SO4 (aq) → 2H+ (aq) + SO42-(aq)
• Triprotic-- 3 H+
Example: H3PO4(aq) →3H+(aq) + PO43-(aq)
Acids
Properties of Acids:
– Litmus Paper—Changed blue to red
– Sour/tart tasting
– Conducts electricity
– React with metals
– React with bases
– Any other properties from lab?
– What common household products fall into Acid
category?
Base
What is a base?
▫ Any compound that contains OH- and that
produce OH- when dissolved in aqueous solutions
 Arrhenius Model Base (Original Definition)
▫ OH- is called the hydroxide ion
Example:
NaOH(aq) → Na+ (aq) + OH-(aq)
NH4OH(aq) → NH4+(aq) + OH-(aq)
Bases
Properties of Bases:
– Bitter Tasting
– Slippery Feeling
– Conduct Electricity
– React with acids
– Litmus paper=turns red paper blue
– Any other properties from lab?
– What common household products fall into base
category?
Agenda 5/13/15
• Acid-Base Warm up
• Collect Red Cabbage Lab
• Notes: Acid-Base definition and Water
• HW: Complete A-B Intro Assignment
Warm-Up
• Use the data to determine the complete rate law
Rate = .041/M2 *s [A]2 [B]
Any questions about the lab?
Warm-Up
• Acid or Base?
▫
▫
▫
▫
▫
NaOH
HCl
KOH
H2SO4
NH3
Warm-Up
• Acid or Base?
▫
▫
▫
▫
▫
NaOH -Base
HCl - Acid
KOH - Base
H2SO4 – Acid (diprotic)
NH3 - ??? W.T. Heck??
Bronsted Definition (Definition 2)
• Observations of H+ and OH- led to alternate definition
of acids and bases known as Bronsted Base and
Bronsted Acid
– Bronsted Acid: Hydrogen Ion Donor
– Bronsted Base: Hydrogen Ion Acceptor
Example:
H20 + NH3 → NH4+ + OH-
• NH4+ now has 4 H+ instead of 3 H+, so it gained H+
• H+ lost by H20, becomes OH• H2O considered Bronsted Acid because it donated the
H+
• NH3 considered Bronsted Base because it accepted the
H+
Water is…
• What is water? Is it an acid or base?
▫ It depends on what it is reacting with
• If H2O reacts with a base…it’s an acid
▫ H2O would lose an H+
▫ Ex: H2O + HCO3- ↔ H2CO3 + OH-`
• If H2O reacts with an acid…it’s a base
▫ H2O would gain an H+
▫ Ex: H2O + HCO3- ↔ CO3-2 + H3O+
Agenda 5/15/15
• Acid-Rain Review
• Discuss pH
• Notes: pH
• Notes: Naming Acids/Bases
• Practice: Naming Acids/Bases
Acid Rain
• With your partners:
▫ What acid(s) make acid rain?
▫ Why is acid rain so dangerous?
▫ What are some innovation we have made to
prevent acid rain?
pH
• What did you learn about pH?
▫ Range?
▫ Scale?
• Did you learn about pOH?
pH Scale
• pH scale from 0-14
▫ pH values greater than 7,
basic
▫ pH values less than 7,
acidic
▫ pH values equal to 7,
neutral
• pH = -log [H+]
▫ To obtain pH of substance,
must take the negative log
of the [H+]
Example:
Given: [H+] = 1.0 x 10-3 M
All you have to do is plug into pH = -log [H+]
pH = -log (1.0 x 10-3 )
pH = 3
Is this acidic, basic, or neutral?
What if given [OH-]?
• Same process, just use pOH = -log [OH-]
Example:
[OH-] = 3.4 x 10-3 M
pOH = -log (3.4 x 10-3 )
pOH = 2.46
• Once we know either the pH or pOH of a
substance, we can calculate the other
pH + pOH = 14
Example:
The pH of a sample of rain in an area with severe
air pollution is 3.5. What is the pOH of the
rainwater?
All you have to do is plug 3.5 into pH…
pH + pOH = 14
3.5 + pOH = 14
pOH = 10.5
• Can also convert from pH or pOH to [H+] or [OH-]
▫ Just have to use pH = -log [H+] and solve for [H+]
Example:
Given : pH = 1.7, find [H+].
Step 1: -pH = -1.7 (always make pH negative)
Step 2: Plug into your calculator, using inverse log
button : 10-1.7
Answer: 2.0 x 10-2 M
Let’s Check how you did
• Using your assignment from yesterday:
▫
▫
▫
▫
Review your answers.
Should any answer be negative?
Should any answer be greater that 14?
Did you solve for [OH-]
Agenda 5/18/15
• Review Acid-Base so far..
▫ pH/pOH
▫ Definition of Acids and Bases
• Notes: Naming Acids/Bases
• Practice: Naming Acids/Bases
▫ White Board practice
• HW: Naming A/B WS
Acid or Base?
•
•
•
•
•
•
•
•
Proton donor
Proton acceptor
Turns red cabbage blue
Turns red cabbage pink
pH lower than 7
pH above 7
Reacts with metals
Feels slippery on your skin
Acid or Base?
•
•
•
•
•
•
•
•
Proton donor ACID
Proton acceptor BASE
Turns red cabbage blue BASE
Turns red cabbage pink ACID
pH lower than 7 ACID
pH above 7 BASE
Reacts with metals ACID
Feels slippery on your skin BASE
pH problem
• If a solution contains 1.0 x 10-2 M of H+ what is
the pOH of this solution?
• Answer: pOH = 12
Essential question
• How can I name either an acid or a base?
How do I name bases?
• NaOH
▫ Sodium Hydroxide
• Ca(OH)2
▫ Calcium hydroxide
• LiOH
▫ Lithium Hydroxide
• Come up with rules with your
neighbors
Nomenclature
• Bases
▫ Already know how to do!
▫ Name of cation, followed by hydroxide
Example
Sodium
Na+ = NaOH = Sodium Hydroxide
Calcium
Ca+2 = Ca(OH)2 = Calcium Hydroxide
Magnesium
Mg+2 = Mg(OH)2 = Magnesium Hydroxide
How do I name acids?
• HCl
▫ Hydrochloric Acid
• HF
▫ Hydrofluoric Acid
• H2 SO4
▫ Sulfuric Acid
• H3 PO4
▫ Phosphoric Acid
• HClO
▫ Hypochlorous Acid
• Come up with rules with your
neighbors.
Nomenclature
• Binary Acids (H+ and monoatomic)
▫ Anything ending with “-ide”
▫ Remove the “-ide” and replace with “-ic”
▫ Rule: hydro (stem) ic acid
• Examples:
▫ Chloride
Cl- = HCl = hydrochloric acid
▫ Sulfide
S-2 = H2S = hydrosulfuric acid
Nomenclature
Ternary Acids :
(H+ and polyatomic anion)
• Anions ending with “-ate”, “ite”
Rule:
name of polyatomic , drop “–
ate”, and add “–ic”
name of polyatomic, drop “ite”, and add “-ous”
Examples:
Nitrate
NO3- = HNO3 = nitric acid
Nitrite
NO2- = HNO2 = nitrous acid
Acetate
C2H3O2- = HC2H3O2 = acetic acid
Hypochlorite
ClO- = HClO = hypochlorous
acid
Agenda 5/19
• Stoich Warm-Up
• Review Naming Acids/Bases HW
▫ HW Quiz
• Household Chemicals Lab
• HW: Finish HH Chemicals Lab
Stoich
2HCl(aq) + 1Mg (s)  1MgCl2 (aq) + 2H+(aq)
Given 6.00 grams of Mg(s) and 20.0 grams of
HCl(aq) which of these chemicals is the limiting
reactant?
Let’s Check our HW
Household Chemical Lab
• Obtain 12 different chemicals (1 at a time)
• Use at least two different methods of indicator to
determine pH.
• May have to use more to determine pH
accurately.
• Goggles must be worn because some of these
chemicals can be harmful.
What is it?
• Turns red cabbage blue.
• Turns red litmus paper blue.
What is it?
• Turns blue paper red
• Turns red cabbage pink
What is it?
• Does not affect blue paper
• Turns PhTh pink
What is it?
• Does not affect red paper
• No color change in PhTh
What is it?
• Does not affect PhTh
• Turns blue paper red
What is it?
• Purple in red cabbage
• Does not change PhTh color
What is it?
• Green in red cabbage
• Does not affect blue litmus paper
What is it?
• Does not change PhTh
• Does not affect blue litmus paper
Agenda 5/20
• Collect Household A/B Lab
• Notes: Kw
• Notes: Strong v. Weak Acid/Base
• Demo: Light Demo
• HW: TBA
What makes an acid strong/weak?
• Are all strong acids dangerous?
• Are all weak acids/bases safe?
Strong and Weak Acids and Bases
Concentrated/Dilute
Strong/Weak
• What does it mean for a
solution to be concentrated?
▫ A large amount of solute
▫ High Molarity
▫ More chemical, less water
• What does it mean for a
solution to be dilute?
▫ A small amount of solute
▫ Low Molarity
▫ Less chemical, more water
• Strong Acid/Base
▫ Ionizes completely in water
(every molecule ionizes)
▫ Completely dissolves
HCl + H20 → H30+ + Cl• Weak Acid/Base
▫ Ionizes only slightly (many
molecules do not ionize)
▫ Does not completely dissolve
HF + H20 → H30+ + F-
Strong/Weak Acids
Strong Acid
Weak Acid
Strong Acids and Bases
• Strong Acids:
▫ HCl, HBr, HI, HNO3, H2SO4, HClO4
▫ Can assume [H+]= [acid] because it
completely dissociates
• Strong Bases:
▫ LiOH, NaOH, KOH, Ca(OH)2, Sr(OH)2, Ba(OH)2
▫ Assume [OH-] = [base] because it
completely dissociates
• All other acids and bases are weak!!
Weak Acids
• Acid Dissociation Constant (Ka)
▫ A measure of how strong or weak an acid is.
▫ Expressed using equilibrium constant (remember
those?!?!)
HX(aq) + H20(l)
H30+ (aq) + X- (aq)
Ka= [H30+ ] [X-]
[HX]
OR
HX(aq)
H+(aq) + X-(aq)
Ka = [H+] [ X-]
[HX]
The larger the value of Ka, the stronger the acid!
Weak Acids
• Example:
HClO2(aq) ↔ H+(aq) + CHO2-(aq)
Ka = [H+] [CHO2- ]
[HClO2]
Ka = 1.8 x 10-4
If a different acid, HC2H3O2, is found to have
Ka= 1.8 x 10-5, which is the stronger acid?
Weak Bases
• Weak Base + Water ↔ (conjugate acid) + OHExample: H20(l) + NH3 ↔ NH4+ + OH• Base Dissociation Constant (Kb)
▫ Ratio of conjugate acid and OH- to weak base
Example (from above):
Kb= [NH4+] [OH-]
[NH3]
Strong/Weak Acid Tests
Solution
1
Distilled H2O
2
1 M HCl
3
1 M NaOH
4
1 M HC2H3O2
Reaction
Lite
Brightness
Keq for water is…?
• Keq = [H+][OH- ]
• Keq always equals 1.0 x 10-14
• If [H+ ] = [OH- ] then
substance is neutral
• [H+] > [OH-] is an acidic
solution
• [H+] < [OH-] is a basic
solution
Example:
Determine if the following is an acid, base, or neutral
substance: [H+]= 4 x 10-11 M
We know that Kw= [H+] [OH-] = 1.0 x 10-14
So, all we have to do is substitute in known concentration…
[4 x 10-11M][OH-] = 1.0 x 10-14
[OH-] = 2.5 x 10-4 M
Answer: Base.
Agenda 5/20
• pH Warm-Up
• Notes: Kw
• Practice: Kw
• Notes: Titration
• Practice: Titration
• Demo: Titration Lab for Friday
pH and pOH
• There is a solution of .15M HCl. What is the
[OH-] of this solution?
• Ans: [OH-] = 6.7 x 10-14 M
• Well that was not very fun..
Keq for water is…Kw
• KW = [H+][OH- ]
• KW always equals 1.0 x 10-14
• If [H+ ] = [OH- ] then
substance is neutral
• [H+] > [OH-] is an acidic
solution
• [H+] < [OH-] is a basic
solution
Example:
Determine if the following is an acid, base, or neutral
substance: [H+]= 4 x 10-11 M
We know that Kw= [H+] [OH-] = 1.0 x 10-14
So, all we have to do is substitute in known concentration…
[4 x 10-11M][OH-] = 1.0 x 10-14
[OH-] = 2.5 x 10-4 M
Answer: Base.
Let’s Practice this
• Finish this practice in your seats.
• I will collect it in 10 minutes.
Highway Tragedy
• http://www.wtsp.com/video/1581292146001/1/
1000-gallons-of-sulfuric-acid-spill-on-Highway
Neutralization!
A truck spills 80,000 liters of 3.0 M sulfuric acid on
the highway. A 6.0 M solution of sodium hydroxide
will be used to “clean up” the spill. How many liters
of NaOH will be needed for the job?
H2SO4 + 2 NaOH  Na2SO4 + 2 H2O
• Hint: this is a stoich problem!!
• How many moles of H2 SO4 ?
• How many moles of NaOH do you need?
• How many liters of NaOH is that?
• Neutralization Reaction
▫ An acid and a base react to produce H20 and a salt
Example:
HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
If given the reactants can you determine the products? (don’t
forget to balance!)
Try: HNO3(aq) + Mg(OH)2(aq)
Answer:
2HNO3(aq) + Mg(OH)2(aq) → Mg(NO3)2(aq) + 2H20(l)
Titrations!
Titration is a process that allows us to determine the
concentration of an unknown solution.
Standard Solution – Solution of known concentration
Unknown Solution – Solution where concentration is not known
Endpoint – Point at which perfect neutralization has been
reached
Indicator – Substance used to “reveal” the endpoint
Back-titrating – If we miss the endpoint, we can back-titrate by
adding more of the unknown solution
Titration
• How can you tell when end point has been reached?
▫ Indicator changes color
▫ For strong acid-strong base titration, pH = 7
▫ When neutralized : mol H+ = mole OH-
Titration Calculations
• When neutralized, mol H+ = mol OH▫ MAVA=MBVB
▫ Looks just like our dilution equation!!
• Note: When not 1 H+ or 1 OH-, must multiply
concentration of acid or base for M by #
• Example:
H2SO4 has 2Hs so it takes twice as much NaOH to
neutralize it!!
Agenda 5/22/15
• Titration Lab
• You must collect all data today!!
• We can finish writing up lab on Monday!
Titration Lab
• You must use the same Base the entire time!
• Part 1: Two trials to determine [NaOH]
▫ 10ml acid in flask
▫ 2 drops phth
▫ Drops of base until LIGHT PINK, NOT DARK PINK
• Part 2: Two trials to determine [HCl]
▫ .50 grams of unknown in 50 mL distilled water
▫ 2 drops phth in with acid
▫ Drops of base until LIGHT PINK, NOT DARK PINK
• DO NOT FORGET TO ADD THE PhTH
▫ Please add this to the flask, not the buret!!
• Make a data table on the back of your lab
Data Table Example
Part 1
Initial HCl
Final HCl
Initial NaOH
Final NaOH
Initial NaOH
Final NaOH
Calculated [NaOH]:________
Trial 1
Trial 2
Part 2
Trial 1
Calculated
_________
moles of NaOH
Trial 2
Calculated moles _________
of NaOH
Agenda 5/26/15
• Titration Warm-Up
• Recap Lab from Friday
▫ Complete Lab and Data Table
• Titration Practice Problems
• Review Acid/Base Chemistry for Test tomorrow
• HW: Study for Test Tomorrow!!
Data Table Part I
Part 1
Initial HCl
Final HCl
Initial NaOH
Final NaOH
Trial 1
0.00
10.50
0.00
9.80
Trial 2
10.50
11.10
9.80
19.00
Part 2
Initial NaOH
Final NaOH
Calculated [NaOH]: ????????
Trial 1
Calculated
_________
moles of NaOH
Trial 2
Calculated moles _________
of NaOH
Data Table Part II
Part 1
Initial HCl
Final HCl
Initial NaOH
Final NaOH
Trial 1
0.00
10.50
0.00
9.80
Trial 2
10.50
11.10
9.80
19.00
Part 2
Initial NaOH
Final NaOH
Calculated [NaOH]: ????????
Trial 1
0.00
14.60
Calculated
_________
moles of NaOH
Trial 2
14.60
30.00
Calculated moles _________
of NaOH
Hints for Calculations
• Remember:
▫ MaVa = MbVb
▫ Neutralization occurs when moles acid = moles base
▫ Molar Mass: # of moles / gram of chemical