The document discusses several key concepts regarding acids, bases, and salts: - The larger the Ka value of an acid, the stronger the acid. The larger the Kb value of a base, the stronger the base. - Salts can be acidic or basic depending on whether their conjugate ion is from a weak acid or base. - Buffer solutions resist changes in pH when acids or bases are added by using a weak acid and its conjugate base, or a weak base and its conjugate acid.

1. 19.3
Previously, on HCHEM….
THE LARGER THE Ka THE STRONGER
THE ACID!!
The larger the Kb the more dissociation
occurs, so the stronger the base.
The conjugates of weak acids & bases
are strong.

2. 19.5
Salts can be acidic or basic if one of the
ions is a conjugate of something weak.

3. 19.5
Salts can be acidic or basic if one of the
ions is a conjugate of something weak.
Ex.
NH4Cl is an acidic salt because NH4+ is
the conjugate of a weak base.

4. 19.5
Salts can be acidic or basic if one of the
ions is a conjugate of something weak.
Ex.
NH4Cl is an acidic salt because NH4+ is
the conjugate of a weak base.
NaCH3COO is a basic salt because
CH3COO- is the conjugate of a weak
acid

5. To determine whether a salt solution is acidic
or basic, remember the following rules:
Not because the strong ones give more ions.
In a neutralization weak acids and bases will give all
of their ions because they are neutralized. (shifts
equilibrium towards dissociation)
It is because of the acid/base properties of the
conjugates.

6. Would the following salts create acidic
or basic solutions when dissolved in
water?
NaCl
KC2H3O2
NH4NO3

7. Would the following salts create acidic
or basic solutions when dissolved in
water?
cation anion
from base from acid
NaCl weak weak
KC2H3O2 weak basic
NH4NO3 acidic weak

8. 19.5
Vapors of the strong acid HCl(aq) and
the weak base NH3(aq) combine to
form the acidic white salt ammonium
chloride (NH4Cl).

9. A buffer is a solution that resists changes in
pH when moderate amounts of acids or
bases are added.

10. Buffer solutions are prepared by mixing
a weak acid with its conjugate base
or
a weak base with its conjugate acid

11. Buffer solutions are prepared by mixing
a weak acid with its conjugate base
or
a weak base with its conjugate acid
Buffers can neutralize both OH– and H+
when one of these ions is added to the
buffered solution.

12. A buffer solution can be prepared by
using the weak base ammonia, NH3, and
an ammonium salt, such as NH4Cl.

13. A buffer solution can be prepared by
using the weak base ammonia, NH3, and
an ammonium salt, such as NH4Cl.
• When acid is added, NH3 reacts with H+.
NH3 + H+  NH4+

14. A buffer solution can be prepared by
using the weak base ammonia, NH3, and
an ammonium salt, such as NH4Cl.
• When acid is added, NH3 reacts with H+.
NH3 + H+  NH4+
• If a base is added, the NH4+ ion from the
–
salt reacts with the OH .
NH4+ + OH-  NH3 + H2O

15. Another buffer system contains the weak
acid acetic acid, HC2H3O2, and the salt
sodium acetate, NaC2H3O2.

16. Another buffer system contains the weak
acid acetic acid, HC2H3O2, and the salt
sodium acetate, NaC2H3O2.
• If base is added, the weak acid reacts to
neutralize the addition.
HC2H3O2 + OH-  C2H3O2- + H2O

17. Another buffer system contains the weak
acid acetic acid, HC2H3O2, and the salt
sodium acetate, NaC2H3O2.
• If base is added, the weak acid reacts to
neutralize the addition.
HC2H3O2 + OH-  C2H3O2- + H2O
• If acid is added, the acetate ion from the
NaC2H3O2 will neutralize the added H+.
C2H3O2- + H+  HC2H3O2

18. The buffer capacity is the
amount of acid or base that
can be added to a buffer
solution before a significant
change in pH occurs.