1. Acids, Bases, and Salts

2. Properties of Acids Conduct electricity when in aqueous solution.
Taste tart or sour
Conduct electricity when in aqueous solution.
Can be strong or weak electrolytes in aqueous solution
React with metals to form H2 gas.
React with bases (hydroxides) to form water and a salt.
Ex: Vinegar (acetic acid), citric acid

3. Properties of Acids
Blue litmus paper turns red in contact with an acid.

4. Properties of Acids
Acids have a pH less than 7

5. Properties of Bases Taste bitter. Feel slippery
Conduct electricity when in aqueous solution.
-Can be strong or weak electrolytes in aqueous solution
React with acids to form water and a salt
Ex: Sodium hydroxide (lye or Drano), Magnesium hydroxide (Milk of Magnesia) Calcium hydroxide (lime water)

6. Properties of Bases
Red litmus paper turns blue in contact with a base.
Phenolphthalein turns pink in a base.
Reference Table M

7. Bases have a pH greater than 7
Properties of Bases
Bases have a pH greater than 7

8. Bases neutralize Acids
Properties of Bases
Bases neutralize Acids
Milk of Magnesia contains magnesium hydroxide, Mg(OH)2, which neutralizes stomach acid, HCl.
2 HCl + Mg(OH)2
MgCl2 + 2H2O
Acid
Base
Notice – a salt and water

9. Hydrogen Ions from Water
HOH ↔ H+ + OH-
At room temperature the molar concentration:
hydrogen ions = 1 x 10-7 M
hydroxide ions = 1 x 10-7 M
In pure water the concentration of H+ and OH- are equal
An aqueous solution in which [H+] and [OH-] are equal is a neutral solution

10. Hydrogen Ions from Water
HOH ↔ H+ + OH-
Acidic solution
[H+] is greater than [OH-]
[H+] of an acidic solution is greater than 1 x 10-7 M
Basic solution (AKA alkaline solution)
[H+] is less than [OH-]
[H+] of an alkaline solution is less than 1 x 10-7 M

11. pH means power of hydrogen
The pH Scale
The pH scale was devised to easily show how acidic or basic a solution is.
Used to express the hydrogen ion concentration
pH means power of hydrogen
pH : [H+] : [OH-] : more acidic
pH : [H+] : [OH-] : more basic or
alkaline.

12. 100
10-1
10-3
10-5
10-7
10-9
10-11
10-13
10-14
[H+] 1 3 5 7 9 11 13 14 pH
Acidic
Neutral
Basic 1 3 5 7 9 11 13 14
pOH
Basic
100
10-1
10-3
10-5
10-7
10-9
10-11
10-13
10-14
[OH-]

14. The pH Scale In an acidic solution, pH < 7
In a basic solution, pH > 7
pH = -log[H+]
pH = -log(1 x 10-7)
pH = 7
pH = -log(1 x 10-9)
pH = 9

15. Practice with the pH Scale
What is the pH of a solution with [H+] = 1 x 10-2?
What is the [H+] of a solution with a pH of 8?
What is the [H+] of a solution with a pH of 9?
The concentration of H+ in a solution with a pH of 8 is ___ times greater than the H+ concentration in a solution with a pH of 9?
The [H+] in a solution with a pH of 2 is ___ times greater than the [H+] in a solution with a pH of 4? 2
1 x 10-8
1 x 10-9 10
100

16. Measuring pH Indicators Substances that change color
Why measure pH?
Maintaining proper acid-base balance in swimming pools, creating proper soil conditions for plant growth, and making medical diagnosis
How do we measure pH?
Sometimes we can use indicators, other times we might need a pH meter
Indicators
Substances that change color
to show whether a substance
is an acid or base
See Reference Table M for
a list of Indicators

17. Measuring pH
2. Compare the color to the chart on the vial – read the pH value.
1. Moisten indicator strip with a few drops of solution, by using a stirring rod.

18. Neutralization Reactions
Remember, in a neutral solution [H+] = [OH-]
So, if I mix a strong acid containing a certain number of H+ ions with strong base that has an equal number of OH- ions, a neutral solution results
Strong Acid with:
1000 H+ ions
Strong Base with:
1000 OH- ions
[H+] = [OH-]:
Neutral solution
HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l)
H2SO4(aq) + 2KOH(aq)  K2SO4(aq) + 2H2O (l)

19. Neutralization Reactions
Neutralization reactions produce water and a salt.
Acid + Base  Water + Salt
The salt forms from an anion from the acid and a cation from the base.
HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l)
H2SO4(aq) + 2KOH(aq)  K2SO4(aq) + 2H2O (l)
water
base
salt
acid
base
water
acid
salt

20. Applications of Neutralization Reactions
Properties related to every day:
Antacids depend on neutralization
Farmers use these reactions to control soil pH
Human body kidney stones from insoluble salts from neutralization reactions
Acid + Base  Water + Salt

21. Titration
We use neutralization reactions to determine the concentration of an acid (or base) in a solution.
Remember that indicators indicate the pH by the color they turn.
Often we use phenolphthalein
It is colorless in neutral and acidic solutions
Pink in basic solutions

22. How to Titrate an Unknown Acid
A titration is a neutralization reactions.
Here’s how it works:
Notice it’s clear
I have .2 liters of NaOH (base)
but I don’t know how concentrated it is…
…in other words I don’t know its molarity (moles/liter)

23. How to Titrate an Unknown Base
Dropper with phenolphthalein
I want to know the molarity of this base, so I do a titration…
Step 1:
Add a few drops of phenolphthalein
This solution is basic, so it will turn pink when I add phenolphthalein
Notice it’s pink

24. How to Titrate an Unknown Base
Step 2:
Using a burette filled with a acid, slowly add acid to the beaker
I need to know the molarity of the acid.
I need to know the volume of the acid.
Lets use 1 molar HCl for this example
Burette filled with a acid (1M HCl)

25. How to Titrate an Unknown Base
Step 3:
When the solution in the beaker just barely changes color – STOP
you have just reached the equivalence point
(moles of H+ = moles of OH-)
What does the (just barely)
color change mean?
Solution has just barely reached the point where it is not longer basic, it is neutral, but not acidic
Remember: phenolphthalein will change to colorless to indicate a neutral or acidic solution
Burette filled with an acid (1M HCl)

26. How to Titrate an Unknown Acid
Burette filled with a acid (1M HCl)
Step 4:
Record how much of the acid went from the burette into the beaker.
For this example, let’s say I used .15 liters of HCl
Step 5:
Use the titration equation to determine the molarity of the unknown base

27. Titration Equation MAVA = MBVB MH+VH+ = MOHVOH
This equation is found on Table T
MAVA = MBVB
MA = MAcid = molarity of H+
MB = MBase = molarity of OH-
The equation is actually
MH+VH+ = MOHVOH

28. Titration Equation MH+VH+ = MOHVOH
In the above equation the M values are for [H+] & [OH-] not the molarity of the acids or bases

29. Using Titration Equation for our Example
Remember: I used
.15L of 1M HCl (acid)
to neutralize
.2L of ? M NaOH (base)
MH+VH+ = MOHVOH
(1M)(.15L) = (MOH)(.2L)
(.15) = .2MOH
.15 / .2 = MOH
.75 moles of OH- per liter of solution
The base is NaOH, there is:
1 “OH” in every 1 “NaOH” so…
It is also .75 moles of NaOH per liter

30. moles of H+ vs moles of Acid moles of OH- vs moles of Base
Some acids have two or more moles of H+ for every mole of acid.
H2SO4 has 2 moles of H+ for every 1 mole H2SO4
Thus, 1.0M H2SO4 has 2.0M H+
The same is true for bases.
Ba(OH)2 has 2 moles of OH-
thus 1.0M Ba(OH)2 has 2.0M OH-

31. Titration Practice Problem
If 15.0 ml of 2.00M H2SO4 titrates 3.00M NaOH, what was the volume of NaOH?
MH+VH+ = MOHVOH
(4)(15) = (3)(VOH)
(60) = (3)(VOH)
60/3 = VOH
20mL = VOH
2.00M H2SO4 has 4.00 MH+ because every 1 mole H2SO4 has 2 moles H+. Likewise, every 1 mole NaOH has only 1 mole OH-.
FOR THIS PROBLEM - Molarity of NaOH solution is same as Molarity of OH-

32. Titration Practice Problem
If 25.0 ml of 2.00M HCl titrates 30.0ml of NaOH, what is the molar concentration of NaOH?
2.00M HCl has 2.00 MH+ because every 1 mole HCl has 1 mole H+. Likewise, every 1 mole NaOH has 1 mole OH-.
FOR THIS PROBLEM - Molarity of solution is same as Molarity of H+ and OH-
(25 ml)(2.00 M) = (30 ml)(x)
x = 1.67M
ANSWER: 1.67 MOH- = 1.67 moles OH-/ 1 Liter

33. Naming Acids Binary Acids Ternary Acids Hydro – anion name – ic acid
ex: HF hydrofluoric acid
Ternary Acids
Named for the polyatomic anion
-ate ending becomes –ic
-ite ending becomes –ous
ex: Sulfuric acid

34. Videos
*Intro video (1:24 min):
Acids & Bases with Hannah & Kelsie (~3 min):
Puppet Acid & base Video(6:56 min):
Richard Thorpe Acids & Bases: (~3:30 min):
*Rainbow Connection with the Muppets(~3:22 min): (man)
(female)
Acid / base Indicators: (4:11 min)
How to do a Titration Experiment(~2min):
World of Chemistry (the Proton in Chemistry (29:05 min):
*Neutralization reaction: (59 sec0
Acid / base Neutralization: (3:23 min)
Acid & Bases have two different Faces: (3:26 min)
Titrating an Acid (3:22 min)
*Titration of an Acid (1:22 min)
How to Perform a titration: (6:07 min)
Cool Universal Indicator Video (1:52 min)