1. Acids & Bases
Chemistry.
Ms. Siddall.

2. Standard 5a: Properties
Acid
Base
Taste
Sour (lemon)
Bitter (soap)
Touch
Like water
Like soap
Reaction with metal
Vigorous
No reaction
Conductivity
Conducts electricity
Litmus Paper
Blue  red
Red  blue
Neutralization
Acid + base  salt + water
e.x. HCl + NaOH  NaCl + H2O
e.x. HCl + Mg 
H2(g) + MgCl2

3. Summary 1
Write the balanced equation for the reaction of aluminum with HCl to form hydrogen and aluminum chloride.
A substance turns red litmus blue and does not react with metal. What is it?

4. Standard 5b: Brønsted-Lowry Definition
Acids donate hydrogen ions
(Hydrogen ion = H+ = proton)
e.x. HBr + H2O  H3O+ + Br-
Bases accept hydrogen ions
e.x. NH3 + H2O  NH4+ + OH-

5. Summary 2
Write the balanced equation for the reaction of HF (hydrofluoric acid) with water.

6. Strong acid ionization
weak acid ionization

7. Standard 5c: Dissociation
Acids:
Strong acid = strong electrolyte
Strong electrolyte = 100% dissociation
e.x HNO3 + H2O  H3O+ + NO3-
in solution
(H3O+ = hydronium ion)
You MUST know these strong acids:
HCl, HBr, HI, HNO3, H2SO4 0%
100%

8. Summary 3 Which of the following are strong acids?
H2SO4, HSO3, HClO2, HBr, HNO3, HNO2

9. Standard 5c: continued Weak acids = weak electrolytes
Weak electrolyte = Partial dissociation
(= equilibrium)
e.x HCN + H2O  H3O+ + CN-
In solution
All other acids are weak acids
Examples: acetic acid HC2H3O2, carbonic acid H2CO3, HCN, H3PO4
~97%
~3%

10. Summary 4
At equilibrium does a weak acid solution contain mostly products or mostly reactants?
At equilibrium does a strong acid solution contain mostly products or mostly reactants?

11. Conjugate acids & bases:
Standard 5c: continued
Conjugate acids & bases:
e.x. HF + H2O  H3O+ + F-
acid
Donates hydrogen ion
Conjugate base
Different from acid by a proton
Base
Accepts hydrogen ion
Conjugate acid
Different from base by a proton CB A B CA

12. Summary 5 HNO3 + H2O  H3O+ + NO3-
Label the acid (A), base (B), conjugate acid (ca), and conjugate base (cb) in the following reaction:
HNO3 + H2O  H3O+ + NO3-

13. Conjugate acids & base pairs:
e.x. HF + H2O  H3O+ + F-
Acid and Conjugate base pair = HF & F-
A strong acid has a weak conjugate base
A weak acid has a strong conjugate base
Base and conjugate acid pair = H2O & H3O+
A strong base has a weak conjugate acid
A weak base has a strong conjugate acid

14. Summary 6
HF + H2O  H3O+ + F-
Identify the acid and conjugate base. Label each as ‘weak’ or ‘strong’
Identify the base and conjugate acid. Label each as ‘weak’ or ‘strong’

15. pH measures the concentration (amount) of H3O+ ions in solution
Standard 5d: pH scale
Definition:
pH = -log[H3O+]
pH measures the concentration (amount) of H3O+ ions in solution

16. Summary 7
Write the equation for HCl reacting with water to make a hydronium ion and a chloride ion
Is the concentration of hydronium ions in this solution high or low?

17. acidic neutral basic pH0 pH1 pH2 pH3 pH4 pH5 pH6 pH7 pH8 pH9 pH10 pH11

18. Summary 8 Provide an example of: An acidic compound A basic compound
A neutral compound
Add a minimum of 3 acids and 3 bases to your pH scale

19. Self ionization of pure water
H2O + H2O  H3O+ + OH-
= Equilibrium system
For pure water: [H3O+] = [OH-] = 1x10-7M
pH = -log[H3O+] = 7
pH 7 = neutral
[H3O+] > [OH-] = pH < 7= acidic solution
[H3O+] < [OH-] = pH > 7 = basic solution

20. Summary 9
Identify the following solutions as acidic, basic, or neutral:
pH 3
pH 5
pH 10
pH 7

21. Acids ‘produce’ H3O+ in solution pH measurement:
e.x. HCl + H2O  H3O+ + Cl-
pH measurement:
[H3O+] = 0.1M = 1x10-1M
pH = -log [H3O+] = -log [1x10-1]
pH = 1
High [H3O+] = ‘Low’ pH reading
= acidic solution

22. Summary 10
pH measures the concentration of ___________________ ions in solution.
A solution with pH = 2:
has a high / low concentration of these ions
is acidic / basic

23. Bases ‘decrease’ H3O+ in solution pH measurement:
e.x. NaOH + H3O+  Na+ + 2H2O
pH measurement:
[H3O+] = 1x10-14M
pH = -log [H3O+] = -log[1x10-14]
pH = 14
Low [H3O+] = ‘High’ pH reading
= basic solution (Alkaline)

24. Summary 11
What is the hydronium ion concentration for a solution with pH = 12?
Is the solution acidic or basic?

26. pH = -log[H3O+] 5f: calculate pH Example: [H3O+] = 4.5 x10-5M
pH should be between 4 - 5
pH = -log[4.5x10-5] = 4.35

27. Summary 13
Estimate then calculate the pH for a solution with:
[H3O+] = 7 x 10-2 M
[H3O+] = 2.2 x 10-9 M

28. pOH = -log[OH-] pOH + pH = 14 Relationship between [OH-] and [H3O+]
Example:
[OH-] = 1x10-2M
pOH = -log[1x10-2] = 2
pH = = 12

29. Summary 14
Complete the following table:
[H3O+]
[OH-] pH
pOH
10-5M 1

30. 5e: acid/base definitions
Arrhenius:
acids are hydrogen containing compounds that ionize to yield H+ ions in aqueous solution.
e.x. HCl(aq)  H+(aq) + Cl-(aq)
Bases ionize to yield OH- ions in aqueous solutions.
e.x. NaOH(aq)  Na+(aq) + OH-(aq)
Problems: NH3 is not a base according to Arrhenius

31. Summary 15
Explain why NH3 is not a base according to the Arrhenius definition of a base.

32. Base = hydrogen acceptor
BrØnsted-Lowry:
Acid = hydrogen donor
Base = hydrogen acceptor
e.x. NH3(aq) +H2O  NH4+ + OH-

33. An acid accepts a pair of electrons (accepts a negative charge)
Lewis:
An acid accepts a pair of electrons (accepts a negative charge)
Acid = proton donor = electron acceptor
A base donates a pair of electrons
Base = proton acceptor = electron donor
e.x. HCl + H2O  H3O+ + Cl-

34. Electron acceptor

35. Electron donor

36. Summary 16
Explain the difference between the Bronsted-Lowry definition and the Lewis definition of acids and bases

37. 5g: buffers
Buffer = a solution whose pH does not change (much) when acid or base are added.
A buffer is a solution made from an acid and its conjugate base

38. There are 2 buffer systems in human blood: H2PO4-/HPO42- & H2CO3/HCO3-
Example: human blood must have a pH between 7.35 – 7.45 (or we will die)
There are 2 buffer systems in human blood: H2PO4-/HPO42- & H2CO3/HCO3-
B- + H2PO4-  HPO42- + HB
B- + H2CO3  HCO3- + HB
HB = acid (H+ donor)
B- = base (H+ acceptor)

40. Summary 17
Write a general equation showing the buffering ability of HSO4- and its conjugate base. (use B- as the base that reacts with HSO4-)