Unit 13 : Unit 13 Acids and Bases
Slide 2 : Properties of acids and bases? Acids
react with carbonates
react with metals
turn blue litmus red
sour
neutralize bases Bases
turn red litmus blue
bitter
slippery to touch
neutralize acids What are acids and bases?
Slide 3 : What common substances are acids?
bases? Acids Bases What are acids and bases?
What are acids and bases? : What are acids and bases? Acids are substances that produce
hydronium ions (H3O+) when dissolved in
water. ACID + H2O ? H3O+ EXAMPLE
HCl + H2O ? Cl- + H3O+
What are acids and bases? : What are acids and bases? EXAMPLE
Write the chemical equation showing
what happens when each of the following
acids is dissolved in water:
HF
HNO3
H2SO4
What are acids and bases? : What are acids and bases? Bases are substances that produce
hydroxide ions (OH-) when dissolved in
water. EXAMPLE
NaOH ? Na+ + OH-
What are acids and bases? : What are acids and bases? EXAMPLE
Write the chemical equation showing
what happens when each of the following
bases is dissolved in water:
KOH
Mg(OH)2
Ba(OH)2
Review from last time : Review from last time 1) In general, what kinds of things are acids and bases?
2) Give 3 properties of acids and bases.
3) Write the equation for what happens when the following dissolve in water:
a) HCl
b) NaOH
4) In your own words describe what acids and bases are. [use the terms Hydronium ion, hydroxide ion, hydrogen, lose]
What are acids and bases? : What are acids and bases? Can you tell whether a substance is an
acid or base by looking at its chemical
formula? Any ideas?
What are acids and bases? : What are acids and bases? EXAMPLE
Identify each of the following substances as
either an acid or a base:
LiOH
H2CO3
H3PO4
Naming acids and bases? : Naming acids and bases? To name an acid:
1) Look at the anion in the formula.
a) If the anion is a single ion (Cl-, F-,
Br- ), acid name will begin with hydro
and end in -ic.
b) If anion is a complex ion, the acid
name doesn’t begin with hydro.
Naming acids and bases? : Naming acids and bases? EXAMPLE
Name the following acid:
HF
Naming acids and bases? : Naming acids and bases? EXAMPLE
Name the following acid:
HF
Anion is single ion, therefore we write:
Hydro_____ ic acid Fluorine fluor
Naming acids and bases? : Naming acids and bases? EXAMPLE
Name the following acid:
HNO3
Naming acids and bases? : Naming acids and bases? EXAMPLE
Name the following acid:
HNO3
Anion is a polyatomic, so no hydro prefix: ____ ic acid Nitrate Nitr
Naming acids and bases? : Naming acids and bases? Try these
Name the following acids:
1. HCl
2. HBr
3. H2SO4
4. H3PO4
Naming acids and bases? : Naming acids and bases? To name a base:
1) Identify cation and anion (always hydroxide).
2) Write name of cation first and name of anion second.
Naming acids and bases? : Naming acids and bases? EXAMPLE
Name the following base:
NaOH
Naming acids and bases? : Naming acids and bases? EXAMPLE
Name the following base:
NaOH
Cation = sodium
Anion = hydroxide
Name: Sodium hydroxide
Naming acids and bases? : Naming acids and bases? Try these
Name the following bases:
1. KOH
2. Ca(OH)2
What is pH? : What is pH? pH is a measure of how acidic or basic a
solution is.
The higher the concentration of acid (H3O+), the
more acidic a solution is.
The higher the concentration of base (OH-), the
more basic a solution is.
What is pH? : What is pH? What is concentration?
What is pH?? : What is pH?? EXAMPLE
Which solution in each pair is more acidic?
a) 1M HCl or 2M HCl
b) 3M HCl or 30M HCl
c) 2moles HCl in 1L solution or 2 moles HCl in 2L solution
d) 4 moles HCl in 1L solution or 5 moles HCl in 1L solution
What is pH? : What is pH? EXAMPLE
Which solution in each pair is more basic?
a) 1.5M NaOH or 0.5M HCl
b) 10M NaOH or 12M NaOH
c) 0.1moles KOH in 1L solution or 10 moles KOH in 100L solution
d) 5 moles KOH in 5L solution or 10 moles KOH in 2L solution
What is pH? : What is pH? pH scale runs from ____ to ____.
A pH of 1 means the concentration of
H3O+ is 10-1 M or 0.1M.
A pH of 2 means the concentration of
H3O+ is 10-2 M or 0.01M.
What is the concentration of H3O+ in a solution
of pH 3?
What is pH? : What is pH? For the pH of basic solutions:
When concentration of OH- is 0.1M the
pH of the solution is 13.
When concentration of OH- is 0.01M the
pH of the solution is 12.
What is the pH of a solution that has a
OH- concentration of 0.001M?
Slide 27 : Fill-in the following table
What is pH? : What is pH? pH is a measure of how acidic or basic a
solution is.
The lower the pH the higher the concentration
of H3O+ and the lower the OH- concentration.
The higher the pH the lower the concentration
of H3O+ and the higher the OH- concentration Why are H3O+ and OH- linked? Why does one going
up make the other one go down?
What is pH? : What is pH? It is because water is at equilibrium with its ions.
For K to remain constant if H3O+ goes up than OH-
must go down and vice versa. 2H2O H3O+ + OH- K = [H3O+ ] [OH-]
[H2O]
What is pH? : What is pH? K = [H3O+ ] [OH-] The product of H3O+ and OH- is always equal to 10-14 10-14 = [H3O+ ] [OH-]
What is pH?? : What is pH?? EXAMPLE
Calculate the OH- concentration in solutions
with the following H3O+ concentrations:
a) [H3O+] = 10-7M
b) [H3O+] = 10-6M
c) [H3O+] = 10-13M
d) [H3O+] = 10-10M
What is pH?? : What is pH?? SOLUTION
a) What is OH- concentration in solution
with the H3O+ concentration = 10-7M?
We said the product of [H3O+ ] and [OH-]
must equal what? 10-14 = [H3O+ ] [OH-]
What is pH?? : What is pH?? SOLUTION
a) What is OH- concentration in solution
with the H3O+ concentration = 10-7M?
Plug in the value of H3O+ and solve for OH- 10-14 = [H3O+ ] [OH-] 10-14 = [10-7M] [OH-] 10-7 = [OH-]
What is pH? : What is pH? Key points up until now:
1) pH is related to concentration of H3O+ and OH-
2) The concentrations of H3O+ and OH- are related
What is pH?? : What is pH?? pH is based on the powers of 10 in [H3O+]
concentration.
What is pH? : What is pH? EXAMPLE
Calculate the pH’s of the solutions with the
following [H3O+] concentrations :
a) [H3O+] = 1M
b) [H3O+] = 0.1M
c) [H3O+] = 2.5M
d) [H3O+] = 10-7M
What is pH? : What is pH? pOH or the powers of OH- is calculated
almost exactly the same way .
Slide 38 : EXAMPLE
Calculate the pOH’s of the solutions with the
following [OH-] concentrations :
a) [OH-] = 10-7M
b) [OH-] = 10-3M
How could you calculate the pH of these
solutions? What is pH?
What is pH? : What is pH? How can we calculate the pH of a solution
when we are given [OH-] concentrations?
2 ways: 1. Calculate [H3O+] and then pH
or 2. Calculate pOH and use the following
relationship: pOH + pH = 14
Slide 40 : EXAMPLE
Calculate the pH’s of the solutions with the
following [OH-] concentrations :
a) [OH-] = 10-7M
b) [OH-] = 10-3M What is pH?
Slide 41 : Solution
Calculate the pH’s of the solutions with the
following [OH-] concentrations :
a) [OH-] = 10-7M
step 1: pOH = -log [OH- ]
pOH = -log [10-7M]
pOH = 7 What is pH?
Slide 42 : Solution
Calculate the pH’s of the solutions with the
following [OH-] concentrations :
a) [OH-] = 10-7M
step 2: pOH + pH = 14
7 + pH = 14
pH = 7 What is pH?
What is pH? : What is the concentration of H3O+ in a pH 7
solution? What is pH? EXAMPLE Another type of problem is if you are
given the pH and asked for the concentration.
What is pH? : What is the concentration of H3O+ in a pH 7
solution?
pH = -log [H3O+]
7 = -log [H3O+] What is pH? SOLUTION (X -1) (X -1)
What is pH? : What is the concentration of H3O+ in a pH 7
solution?
pH = -log [H3O+]
7 = -log [H3O+]
-7 = log [H3O+] What is pH? SOLUTION (X -1) (X -1)
What is pH? : What is the concentration of H3O+ in a pH 7
solution?
pH = -log [H3O+]
7 = -log [H3O+]
-7 = log [H3O+] What is pH? SOLUTION (X -1) (X -1) 10 10
What is pH? : What is the concentration of H3O+ in a pH 7
solution?
pH = -log [H3O+]
7 = -log [H3O+]
-7 = log [H3O+]
10-7 = [H3O+] What is pH? SOLUTION (X -1) (X -1) 10 10
What is pH? : What are the H3O+ concentrations of the
solutions with the following pH’s?
1. pH 3
2. pH 5.5
3. pH 3.6
4. pH 11.2 What is pH? Try these
Acids and bases : What are the OH- concentrations of the
solutions with the following pH’s?
1. pH 1.5
2. pH 10.2
3. pH 8.5
4. pH 13.3 Acids and bases Try these
Review from last time : 1. Calculate the pH of a solution with
[H3O+ ] = 2.3 X 10-4
2. a. Calculate the [OH-] for a solution with
[H3O+ ] = 8.7 X 10-12
b. Is the solution in (a) acidic or basic? Explain.
3. a.What is the pOH of a solution with
[OH-] = 3.0 X 10-5
b. What is the pH of the solution in (a)?
4. What is the [H3O+] in a solution of pH 2.4? Review from last time
Acids and bases : Acids and bases Bronsted-Lowry acids and bases
Acids and bases : Acids and bases Another way of looking at it is….
Acids and bases : Acids and bases Another way of looking at it is….
Acids and bases : Acids and bases Another way of looking at it is….
Acids and bases : Acids and bases Another way of looking at it is…. Substances that gain H+ are Bronsted-Lowry bases
Substances that lose H+ are Bronsted-Lowry acids
Acids and bases : Identify the Bronsted acids and bases in each
of the following reactions:
a. HCl + H2O ? H3O+ + Cl-
b. HSO4- + H2O ? H2SO4 + OH-
c. H2CO3 + H2O ? H3O+ + HCO3- Acids and bases EXAMPLE
Acids and bases : Acids and bases When an acid loses H+ it forms a base. NH3 + H2O ? NH4+ + OH- Acid Conjugate base
Acids and bases : Acids and bases When a base gains H+ it forms an acid. NH3 + H2O ? NH4+ + OH- Base Conjugate acid
Acids and bases : Identify the reactants as either acids or bases
and the products as either conjugate acids or
bases:
a. HCl + H2O ? H3O+ + Cl-
b. HSO4- + H2O ? H2SO4 + OH-
c. H2CO3 + H2O ? H3O+ + HCO3- Acids and bases EXAMPLE
Measuring pH : Measuring pH How do we measure pH? Which indicators do you know of?
Measuring pH : Measuring pH There are many other indicators Which color indicates a base?
Which color indicates an acid?
Acids and bases : Acids and bases How indicators work Acid Conjugate base
Acids and bases : Acids and bases How indicators work Yellow Blue
Acids and bases : Acids and bases How indicators work Yellow Blue
Acids and bases : Acids and bases Consider the following indicator HIn + H2O In- + H3O+ Color 1 Color 2 Is the solution acidic or basic right now?
How will color change by adding acid/base?
Acids and bases : Acids and bases Different indicators have different ranges,
meaning they change colors at different
pH’s 7 0 14 Indicator 1 Indicator 2 Indicator 3
Review from last time : Identify the reactants as either acids or bases
and the products as either conjugate acids or
bases:
a. H3O+ + Cl- ? HCl + H2O
b. H3PO4 + OH- ? H2PO4- + H2O Review from last time EXAMPLE
Review from last time : Review from last time Consider the following indicator HIn + H2O In- + H3O+ Color 1 Color 2 What color will the solution be when:
a)acid is added b) base is added
Acids and bases : Acids and bases Strength of acids and bases What is a weak electrolyte? How is it different
than a strong electrolyte?
Which type of electrolyte lights a lightbulb most
brightly?
Acids and bases : Acids and bases Strength of acids and bases Strong acids ionize completely
ex: HCl, HNO3, H2SO4
Weak acids ionize very little
ex: H2CO3, CH3COOH
Review from last time : 1. Name 1 strong acid and 1 weak acid
2. Which type of acid will:
a) light a light bulb most brightly?
b) ionize most completely?
c) have the biggest K for its ionization?
3. Does the following diagram represent a: a) weak acid or b) strong acid. Review from last time
Review from last time : Review from last time 5.
Consider the following indicator HIn + H2O In- + H3O+ Color 1 Color 2 What color will the solution be when:
a)acid is added b) base is added
Review from last time : 6. True or False: All indicators change color at
the same pH.
7. Identify the acid, base, conjugate acid and conjugate base in the following equation:
H3O+ + F- ? HF + H2O
8. Which is the stronger acid?
A. Oxalic acid (K = 5.6 • 10-2 )
B. Carbonic acid (K = 4.8 • 10-11 ) Review from last time
Acids and bases : Acids and bases Strong acids ionize completely H2O HCl Cl- + H+ How would you fix the arrows to best represent
the equilibrium in this reaction?
Acids and bases : Acids and bases The products are favored in this process. HCl Cl- + H+ What can you say about the EQ constant (K) for
this process?
Acids and bases : Acids and bases The reactants are favored in this process H2O HAc Ac- + H+ How would you fix the arrows to best represent
the equilibrium in this reaction?
Acids and bases : Acids and bases Weak acids ionize very little (less than 1%) H2O HAc Ac- + H+ What can you say about the EQ constant (K)
for this process?
Acids and bases : Acids and bases Strength of acids and bases Strong acids ionize completely and have K’s > >1
ex: K for HCl = 1011
Weak acids ionize very little and have K’s <<1
ex: K for CH3COOH = 1.8 X 10-5
Acids and bases : Calculate the pH of the following strong acids
a. 0.5M HCl
b. 3.0 X 10-2M HNO3 Acids and bases EXAMPLE
Acids and bases : Calculate the pH of the following strong acids
a. 0.5M HCl
What will the concentration of H3O+ be
when the concentration of HCl is 0.5M? Acids and bases Solution
Acids and bases : 100 % ionizes so HCl produces 0.5M H3O+ Acids and bases Solution HCl Cl- + H3O+ 0.5M
Acids and bases : 100 % ionizes so HCl produces 0.5M H3O+ Acids and bases Solution HCl Cl- + H3O+ 0M 0.5M 0M
Acids and bases : 100 % ionizes so HCl produces 0.5M
H3O+ Acids and bases Solution HCl Cl- + H3O+ 0.5M 0M 0.5M
Acids and bases : If the concentration of H3O+ is 0.5M than the
pH is given by: Acids and bases Solution pH = -log [H3O+ ]
pH = -log [0.5M]
pH =
Acids and bases : Calculate the pH of the following weak acids
a. 0.5M CH3COOH
b. 3.0 X 10-2M CH3COOH Acids and bases EXAMPLE
Acids and bases : 1% ionizes so CH3COOH produces very little
H3O+ Acids and bases Solution HAc Ac- + H3O+ 0.5M 0M 0M 1% of HAc ionizes, so to find out how much
H3O+ is produced, find what 1% of 0.5M is.
Acids and bases : 1% ionizes so CH3COOH produces very little
H3O+ Acids and bases Solution HAc Ac- + H3O+ 0.495M 0.005M 0.005M 0.01 X 0.5M = 0.005M
0.005M H3O+ is produced.
Acids and bases : If the concentration of H3O+ is 0.005M than
the pH is given by: Acids and bases Solution pH = -log [H3O+ ]
pH = -log [0.005M]
pH =
Review from last time : 1. We can represent the concentrations of all the compounds with bars. If the picture below represents the starting amounts of all the compounds, what would the final concentrations look like if HNO3 is a strong acid? Review from last time HNO3 NO3- + H3O+
Review from last time : 2. A. If you dissolve 1M HNO3 in water what will the final concentrations of NO3- and H3O+ be?
B. What will the pH of this solution be? Review from last time HNO3 NO3- + H3O+ 1M 0M 0M
Review from last time : 3. We can represent the concentrations of all the compounds with bars. If the picture below represents the starting amounts of all the compounds, what would the final concentrations look like if HAc is a strong acid? Review from last time HAc Ac- + H3O+
Review from last time : 4. A. If you started off with 1M Hac, what will the final concentrations of NO3- and H3O+ be?
B. What will the pH of this solution be? Review from last time HAc Ac- + H3O+ 1M 0M 0M
Acids and bases : Acids and bases Key point Given 2 acid solutions of the same
concentration, one strong and the other weak,
the strong acid solution will be more acidic and
have a lower pH.
Acids and bases : Acids and bases Think about this Which is the most dangerous and why?
A. concentrated, strong acid
B. concentrated, weak acid
C. dilute, strong acid
D. dilute, weak acid
Acids and bases : Calculate the pH of the following acid
solutions (assume the weak acid ionizes 1%):
a. 0.015M HCl (strong acid)
b. 0.0025M HNO3 (strong acid)
c. 0.175M CH3COOH (weak acid) Acids and bases Try these
Acids and bases : A 0.1000M solution of Acetic acid is only
partially ionized. From measurements of the
pH of the solution, you conclude that the
[H3O+ ] is 1.34 • 10-3 M. What is the K for
the reaction:
HAc Ac- + H3O+ Acids and bases EXAMPLE
Acids and bases : Step 1: What do you want to find? Acids and bases Solution
Acids and bases : Step 1 : What do you want to find?
K
: What is the equation for K? Acids and bases Solution
Acids and bases : Step 1 : What do you want to find?
K
: What is the equation for K? Acids and bases Solution So what do you need to know to get K?
Acids and bases : You need [H3O+ ], [Ac-] and [HAc] Acids and bases Solution Do you know any of these already? You are given [H3O+ ] = 1.34 • 10-3 M
Acids and bases : Acids and bases Solution Step 2 : find [Ac-] and [HAc].
To do this set up a table
HAc Ac- + H3O+
starting
change
at EQ
Acids and bases : Acids and bases Solution Step 2 : fill in the table
HAc Ac- + H3O+
starting
change
at EQ Are you given any of these?
Acids and bases : Acids and bases Solution Step 2 : fill in the table
HAc Ac- + H3O+
starting 0.1000M
change
at EQ 1.34 • 10-3 M Right when you put 0.1000M HAc in water how much Ac- and H3O+ is there?
Acids and bases : Acids and bases Solution Step 2 : fill in the table
HAc Ac- + H3O+
starting 0.1000M 0M 0M
change
at EQ 1.34 • 10-3 M You start out with 0M for each.
Acids and bases : Acids and bases Solution Step 2 : fill in the table
HAc Ac- + H3O+
starting 0.1000M 0M 0M
change
at EQ 1.34 • 10-3 M How much must the [H3O+ ] have changed to go from 0 to 1.34 • 10-3 M?
Acids and bases : Acids and bases Solution Step 2 : fill in the table
HAc Ac- + H3O+
starting 0.1000M 0M 0M
change +1.34 • 10-3 M
at EQ 1.34 • 10-3 M It went up by + 1.34 • 10-3 M?
Acids and bases : Acids and bases Solution Step 2 : fill in the table
HAc Ac- + H3O+
starting 0.1000M 0M 0M
change +1.34 • 10-3 M
at EQ 1.34 • 10-3 M What do you notice about how much each of the products increases in a reaction- look back.
Acids and bases : Acids and bases Solution Step 2 : fill in the table
HAc Ac- + H3O+
starting 0.1000M 0M 0M
change +1.34 • 10-3 M +1.34 • 10-3 M
at EQ 1.34 • 10-3 M Both products increase by the same amount, so
Ac- must increase by 1.34 • 10-3 M as well.
Acids and bases : Acids and bases Solution Step 2 : fill in the table
HAc Ac- + H3O+
starting 0.1000M 0M 0M
change +1.34 • 10-3 M +1.34 • 10-3 M
at EQ 1.34 • 10-3 M What is the concentration of Ac- at equilibrium then?
Acids and bases : Acids and bases Solution Step 2 : fill in the table
HAc Ac- + H3O+
starting 0.1000M 0M 0M
change +1.34 • 10-3 M +1.34 • 10-3 M
at EQ +1.34 • 10-3 M 1.34 • 10-3 M 0 + 1.34 • 10-3 M = final concentration
Acids and bases : Acids and bases Solution Step 2 : fill in the table
HAc Ac- + H3O+
starting 0.1000M 0M 0M
change +1.34 • 10-3 M +1.34 • 10-3 M
at EQ +1.34 • 10-3 M 1.34 • 10-3 M If the [Ac-] and [H3O+ ] went up by 1.34 • 10-3 M then how much must the [HAc] go down by?
Acids and bases : Acids and bases Solution Step 2 : fill in the table
HAc Ac- + H3O+
starting 0.1000M 0M 0M
change -1.34 • 10-3 M +1.34 • 10-3 M +1.34 • 10-3 M
at EQ +1.34 • 10-3 M 1.34 • 10-3 M - 1.34 • 10-3 M
Acids and bases : Acids and bases Solution Step 2 : fill in the table
HAc Ac- + H3O+
starting 0.1000M 0M 0M
change -1.34 • 10-3 M +1.34 • 10-3 M +1.34 • 10-3 M
at EQ +1.34 • 10-3 M 1.34 • 10-3 M What then is the [HAc] at EQ?
Acids and bases : Acids and bases Solution Step 2 : fill in the table
HAc Ac- + H3O+
starting 0.1000M 0M 0M
change -1.34 • 10-3 M +1.34 • 10-3 M +1.34 • 10-3 M
at EQ 0.0987M +1.34 • 10-3 M 1.34 • 10-3 M 0.1000M - 0.00134M = 0.0987M
Acids and bases : Step 3 : Now use your K expression to
calculate K. Acids and bases Solution K = 0.0000172M Write this
in scientific
notation. = 1.72• 10-5M
Acids and bases : A 0.200M solution of a weak acid is only
partially ionized. From measurements of the
pH of the solution, you conclude that the
[H3O+ ] is 9.86 • 10-5 M. What is the K for
the reaction:
HX X- + H3O+ Acids and bases EXAMPLE 1
Acids and bases : A 0.100M solution of a methanoic acid is only
partially ionized. From measurements of the
pH of the solution, you conclude that the
[H3O+ ] is 4.2 • 10-3 M. What is the K for
the reaction:
HMet Met - + H3O+ Acids and bases EXAMPLE 2
Acids and bases : Acids and bases Neutralization To neutralize a certain number of moles of an
acid in solution you must add, the same number
of moles of base.
To neutralize a certain number of moles of an
base in solution you must add, the same number
of moles of acid.
Acids and bases : 1. How many moles of HCl must be added to neutralize the following amounts of NaOH:
a. 5 moles of NaOH
b. 10 moles of NaOH
c. 0.25moles of NaOH Acids and bases EXAMPLE
Acids and bases : 2. How many moles of KOH must be added to neutralize the following amounts of HNO3:
a. 2 moles of HNO3
b. 8 moles of HNO3
c. 5.25moles of HNO3 Acids and bases EXAMPLE
Acids and bases : 3. How many moles of KOH must be added to neutralize the following HCl solutions:
a. 1L of 4M HCl
b. 2L of 3M HCl
c. 6L of 1M HCl Acids and bases EXAMPLE
Acids and bases : 4. How many moles of HNO3 must be added to neutralize the following NaOH solutions:
a. 1L of 2M NaOH
b. 2L of 2M NaOH
c. 4L of 1M NaOH Acids and bases EXAMPLE
Acids and bases : 5. How many L of 2MHNO3 must be added to neutralize the following NaOH solutions:
a. 1L of 3M NaOH
b. 2L of 10M NaOH
c. 4L of 0.1M NaOH Acids and bases EXAMPLE
Acids and bases : 6. How many L of 0.5M NaOH must be added to neutralize the following HCl solutions:
a. 0.5L of 2M HCl
b. 1L of 5M HCl
c. 2L of 6M HCl Acids and bases EXAMPLE