1. Chapters 9 & 19 Chemistry 1L Cypress Creek High School
Unit 13: Acids & Bases
Chapters 9 & 19
Chemistry 1L
Cypress Creek High School

2. Properties of Acids Taste sour Feel watery
Are electrolytes: conduct an electrical current by forming H+ ions in solution
React with metals
Corrosive
pH < 7 2

3. Arrhenius’ Definition of Acids
Arrhenius defined acids as anything that produces H+ ions in solution
Monoprotic acids – have 1 ionizable hydrogen (HCl)
Diprotic acids – have 2 ionizable hydrogens (H2SO4)
Triprotic acids – you guessed it…they have 3 (H3PO4)
Produces H+ ions in solution 3

4. Bronsted-Lowry Definition of Acids
According to Bronsted-Lowry an acid is a chemical that is able to lose or "donate" a hydrogen ion (aka proton because the H+ contains no electrons or neutrons) during a reaction.
Acid loses a hydrogen ion

5. Naming an Acid hydro ______ic acid ate ions: _________ic acid
Binary acids (H + nonmetal):
hydro ______ic acid
Ternary acids (H + polyatomic ion):
ate ions: _________ic acid
ite ions: _________ous acid
Name the following acids:
HBr
H2SO3
H3PO4
Write the formulas for the following acids:
Hydrosulfuric acid
Nitrous acid
Chromic acid 5

6. Properties of Bases Taste bitter Feel slippery Corrosive
Are electrolytes: conduct an electrical current by forming OH- ions in solution
pH > 7 6

7. Arrhenius’ Definition of Bases
Arrhenius defined Bases as anything that produces OH- ions in solution
Produces OH- ions in solution 7

8. Bronsted-Lowry Definition of Bases
A chemical species that is able to gain or "accept" a hydrogen ion (aka proton because the H+ contains no electrons or neutrons) during a chemical reaction.
Base gains a hydrogen ion

9. Naming a Base Formula is either: Metal + OH- or Ammonium + OH-
Name + hydroxide
Name the following bases:
NaOH
NH4OH
NH3
Ca(OH)2
Write the formulas for the following bases:
Magnesium hydroxide
Aluminum hydroxide 9

10. Conjugates Conjugate acid is formed when a base accepts a proton (H+)
Conjugate base is formed when a acid donates a proton (H+) 10 10

11. Conjugate Acid/Base Pairs
Acids and Bases are always reactants
Conjugate acids and conjugate bases are always products.
Conjugate acid is the product that remains when a base has accepted a proton.
Conjugate base is the product that remains when an acid has donated a proton.
Ex NH3 + H2O → NH4+ + OH-
(base) (acid) (c.acid) (c.base)

12. Conjugate Practice NH3(g) + H3O+(aq)  NH4+(aq) + H2O(l)
CH3OH(l) + NH2-(aq)  CH3O-(aq) + NH3(g)
OH-(aq) + H3O+(aq)  H2O(l) + H2O(l)
NH2-(aq) + H2O(l)  NH3(g) + OH-(aq)
Base
Acid
C.Acid
C.Base
Acid
Base
C.Base
C.Acid
Base
Acid
C.Acid
C.Base
Base
Acid
C.Acid
C.Base

13. Amphoteric
Some substances can act as an acid or a base and are called amphoteric.
Ex. H2O can act as both an acid and a base
NH3 + H2O → NH4+ + OH-
(base) (acid)
H+ was lost by water
HCl + H2O → H3O+ + Cl-
(acid) (base)
H+ was gained by water 13

14. Indicators
Indicators are organic substances that change colors in an acid or a base (sometimes paper, sometimes liquids)
Acids turn…
Litmus paper – red
Phenolphthalein – clear
Universal indicator – yellow/orange/red
Bases turn…
Litmus paper – blue
Phenolphthalein – magenta (hot pink)
Universal indicator – dark green/blue/purple 14

15. The pH Scale
pH is a mathematical scale in which the concentration of hydrogen ions (H+) in a solution is expressed as a number from 0 to 14.
The pH scale is a convenient way to describe the concentration of H+ ions in acidic solutions, as well as the hydroxide ions in basic solutions.

16. pH and pOH Scale
[H+] and [OH-] are inverses: the exponents always add up to -14
Ex: If [H+] = 1.0x10-3 M, then [OH-] = 1.0x10-11 M

17. Household Items & the pH Scale

18. Mathematical Definition of pH and pOH
The letter “p” in front of pH and pOH refers to the negative log.
A logarithm (log) is the power to which a base, such as 10, must be raised to produce a given number.
For example: the logarithm of 1000 to base: 10 is 3, because 3 is the power to which ten must be raised to produce 1000: 103 = 1000

19. pH and pOH
The pH of a solution equals the negative logarithm of the hydrogen ion concentration.
Chemists have also defined a pOH scale to express the basicity of a solution.
In an acidic solution, [H+] > [OH-]
In a basic solution, [H+] < [OH-]
pH + pOH = 14 pH
pOH
Stands for “power of hydrogen”
Stands for “power of hydroxide”
Shows the [H+] in a solution
Shows the [OH-] in a solution
pH = -log[H+]
pOH = -log[OH-]

20. pH and pOH Calculations
Notice the relationship between concentration and the pH/pOH value:
Toothpaste has a hydrogen ion concentration of 10–10M, so its pH is 10.
pH = -log[10-10] = 10
Pure water, which is neutral, has a pH of 7. That means its hydrogen ion concentration is 10–7M.
7 = -log[H+] ; [H+] = 10-7

21. Relating pH, pOH, [H+], & [OH-]4 2
1x10-6
1.26x10-4
9.64
13.7
1.82x10-4 10
1x10-4
1x10-10 12
1x10-12
1x10-2 6 8
1x10-8
10.1
3.9
7.9x10-11
4.36
4.37x10-5
2.29x10-10
0.3
2.00x10-14
5.01x10-1
3.74
10.26
5.50x10-11

22. Strength of Acids and Bases
The terms weak and strong are used to compare the strengths of acids and bases
The terms dilute and concentrated are used to compare the concentration of solutions
They do not mean the same thing!
The combination of strength and concentration determines the behavior of the acid or base.

23. Strength of Acids and Bases
Strength is Determined by how much they ionize (dissociate) in water
Strong – ionize 100% in water
Weak – only partially ionize in water
Complete dissociation - all HCl compounds have separated into H+ and Cl- ions
Partial dissociation - some HNO2 compounds have separated into H+ and NO2- ions, while some remain together 23

24. Strength of Acids and Bases
Strong Acids:
Only HNO3, HI, HBr, HCl, H2SO4, HClO4
Remember: NO, I Brought Claude SOme ClOthes
All other acids are weak, and remain in equilibrium
Ex: HNO2 ↔ H+ + NO2-
Strong Bases: Group I or II metals
Ex: NaOH, Mg(OH)2…etc.
All other bases are weak, and remain in equilibrium
NH3 + H2O ↔ NH4+ + OH- 24

25. Conjugate Strength Strong Acid = weak conjugate base
Strong Base = weak conjugate acid
Weak Acid = strong conjugate base
Weak Base = strong conjugate acid
Example:
HCl + NH3 → Cl NH4+
(strong acid) (weak base) (weak c. base) (strong c. acid) 25

26. Acid-Base Reactions
The reaction of an acid and a base to produce a salt and water is called a neutralization reaction.

27. Neutralization Reactions
Sodium hydroxide (base) and hydrochloric acid (acid) react to form sodium chloride (salt) and water.

28. Neutralization Practice
Neutralizations are double displacement reactions!
Practice predicting products (always a salt and water):
Example #1
__Ca(OH)2 + __H3PO4 → ?
__Ca(OH)2 + __H3PO4 → __Ca3(PO4)2 + __H2O
3Ca(OH)2 + 2H3PO4 → Ca3(PO4)2 + 6H2O
Example #2
__Fe(OH)2 + __HBr → ?
__Fe(OH)2 + __HBr → __FeBr2 + __H2O
Fe(OH)2 + 2HBr → FeBr2 + 2H2O 28

29. Acid-Base Titrations
Titration is used in determining the concentration of an unknown acid or base.
An indicator is added to the standardized acid (acid of known concentration).
The unknown base is added slowly with a burette until the solution is neutralized and reaches the equivalence point (where [H+] = [OH-]).
The equivalence point is not necessarily where pH = 7
Adding one more drop of base changes the color of the solution to pink. This is called the endpoint.

30. Titration Calculations
MaVa(H+)= MbVb(OH-)
Note: pH at the equivalence point is not always 7.
Strong Acid + Strong Base, pH=7
Strong Acid + Weak Base, pH<7
Weak Acid + Strong Base, pH>7
Example: It took 75mL of NaOH to neutralize 50mL of 2M HCl. What is the concentration of the NaOH?
MaVa(#H+) = MbVb(#OH-)
(2M)(50mL)(1) = (x)(75mL)(1)
x = 1.33M NaOH

31. Titration Practice
It took 20mL of Ca(OH)2 to neutralize 25mL of 0.05M HCl. What is the concentration of the base?
MaVa(#H+) = MbVb(#OH-)
(0.05M)(25mL)(1) = (x)(20mL)(2)
x = M