This document discusses acids and bases. It defines strong acids as acids that dissociate completely in water, such as HCl, while weak acids like acetic acid dissociate only slightly. The concentration of H3O+ ions in strong acids equals the concentration of the acid. In weak acids it is much less. Strong bases like NaOH also dissociate completely while weak bases like ammonia dissociate slightly. pH is a measure of H3O+ concentration and indicates if a solution is acidic (pH < 7) or basic (pH > 7). Acid-base reactions involve neutralization of acids by bases to form salts and water. Titration can be used to determine unknown concentrations using indicators and the

1. Acids and Bases

3. Strong Acid (SA)
• an acid that dissociates completely into ions
in water
Ex. All molecules of HCl(aq) dissociate into
H+ and Cl- ions
▫ H+ ions that are formed bond with H2O to form
H3O+
HCl(aq) + H2O(l)  H3O+(aq) + Cl-(aq)

4. Dissociation (Strong Acid)
100% of hydrogen chloride molecules
dissociate

6. Strong Acid Examples
HBr
HI
HNO3
H2SO4
HClO4

7. Weak Acid (WA)
• an acid that dissociates very slightly into
ions in water
Ex. not all molecules of CH3COOH(aq) break
apart, some remain intact
• only about 1% of acetic acid molecules
dissociate

8. Dissociation (Weak Acid)
1% of acetic acid molecules dissociate. In solution
there are mostly acetic acid molecules and only some
ions.

10. Concentration
• the concentration of H3O+(aq) ions, [H3O+],
in a dilute solution of a SA is equal to the
concentration of the acid, [acid]
[H3O+] = [strong acid]
• Ex. In a sample of 1.0 mol/L HCl(aq)
[H3O+] = 1.0 mol/L
Recall: C = n
square bracket V
Molar Concentration

11. Concentration
• the concentration of H3O+(aq) ions, [H3O+],
in a dilute solution of a WA is much less
than the concentration of the acid, [acid]
• Ex. In a sample of 1.0 mol/L CH3COOH (aq)
[H3O+] <<< 1.0 mol/L
• That is, [H3O+] < [weak acid]

12. Strong Base (SB)
• a base that dissociates completely into
ions in water
Ex. all molecules of NaOH(aq) dissociate into
Na+ and OH- ions
• other SB’s are…
KOH
Ca(OH)2
Ba(OH)2

13. Weak Base (WB)
• most bases are weak
• WB dissociates very slightly into ions in
water
▫ Ex. Ammonia  [OH1-] < [weak base]

14. Concentration
• the concentration of OH1-(aq) ions, [OH1-],
in a dilute solution of a SB is equal to the
conc. of the base, [base]
[OH1-] = [strong base]
Ex. In a sample of 1.0 mol/L NaOH(aq)
[OH1-] = 1.0 mol/L

15. pH

16. 16
pH [H3O+ ] [OH- ]
pOH

17. Measuring Strength – pH Scale
• In pure water,
[H3O+] = [OH-] = 1.0 x 10-7 mol/L
• In acidic solution, [H3O+] > [OH-]
• In basic solution, [H3O+] < [OH-]

19. 19
pH and acidity
The pH values of several
common substances are
shown at the right.
Many common foods are
weak acids
Some medicines and many
household cleaners are
bases.

20. Indicators
• An acid-base indicator is a substance that
changes colour in acid and base solutions. It is
used to determine if neutralization is complete.
• ex. litmus
phenolphthalein (phth)
bromothymol blue (BTB)
universal indicator

21. pH Scale Review
• Now that we know when an acid or base is dissolved in
water it will produce either:
▫ OH-
▫ H+
• pH measures the concentration (how many) of H+ in the
solution
• When pH is 7 that means the concentration of OH- is
equal to H+
• When pH is less than 7 we have a higher concentration of
H+
• When pH is bigger that 7 we have a higher concentration
of OH-

22. Acid-Base Reactions

23. Neutralization
• Adding a base to an acid neutralizes the acid’s
acidic properties.
• This is called a neutralization reaction.
▫ Ex. for an upset stomach, use an ANTACID

24. Neutralization
• In general:
ACID + BASE SALT + WATER
H2SO4(aq) + Ca(OH)2(aq)  CaSO4(aq) + 2H2O(l)

25. Example
1. In an experiment, 15.85 mL of HCl(aq) completely
neutralizes 25.00 mL of 0.125 mol/L KOH(aq).
Calculate the concentration of this acid.

26. Example 2
2. What volume of 0.185 mol/L H2SO4(aq) will react
completely with 25.00 mL of 0.225 mol/L KOH(aq)?

27. Learning Check
3. What mass of aluminum hydroxide will react
completely with 27.50 mL of 0.255 mol/L
H2SO4(aq)?

28. Learning Check 2
4. What is the molar concentration of phosphoric
acid if 17.50 mL of this acid reacted with 3.22 g
of magnesium hydroxide?

29. Titration
• lab procedure involving neutralization, used to
determine an unknown concentration
• progressive addition of a solution (called titrant)
from a graduated tube (called burette) to a known
volume or mass of a second solution, until the
endpoint
▫ endpoint is indicated by a colour change of an added
indicator
• at equivalence point, nH+ = nOH-
▫ given the concentration of one sol’n, you can calculate
the concentration of the other sol’n

30. Titration
• Read p468 - 469 to review procedure

31. Homework
• pg 457 Q 1, 4
• pg 462 Q 8, 9
• pg 466 Q 1, 3, 4, 10
• pg 467 Q 13, 16