ACIDS AND BASES general chemistry senior high school.pptx

1. ACIDS AND BASES
GenChem2

2. •What comes in your mind when you hear the word
acid or a base?
•Some associate an acid and a base to a substance that
taste sour and bitter, respectively.

4. •What is
really an
acid and
base?

5. Different
theories
about acids
and bases
•Arrhenius theory
•Bronsted-Lowry theory
•Lewis or electron-pair theory
•are the three theories that
point out a specific
characteristic which defines
an acid and a base.

6. Arrhenius theory
• Svante Arrhenius formulated a
theory that defines an acid
and a base as substances that
when ionize in water produce
hydrogen ions (H+) and
hydroxide ions (OH-).
• However, Arrhenius theory
could not explain why salt
having no H+ or OH- still
exhibit the property of an acid
or a base upon dissolving in
water.

7. In this lesson, we will
define an acid and a base
according to the Bronsted-
Lowry theory.

8. Bronsted-
Lowry’s theory
acids on and
bases
•Johannes Nicolaus
Bronsted, a Danish
chemist, and Thomas
Martin Lowry, an
English chemist,
introduced the
Bronsted-Lowry
theory of acids and
bases

9. •They defined an acid
as a substance that
is capable of
transferring protons,
the positively charge
ion(H+), and a base
as substance
capable of accepting
protons.

10. •Substances that behave based on
the given definition, are classified
as Bronsted acids and Bronsted
bases.
•When an acid reacts with a base, a
proton (H+) will transfer from acid
towards the base.

11. •The product that will be formed
after an acid loses H+ is called the
conjugate base while the product
that will be formed after a base
accepts H+ is called the conjugate
acid.

12. • In the reaction of HCl and NH3, as shown in Figure 1, HCl donates hydrogen
ion (H+) towards ammonia (NH3) forming ammonium ion (NH4+), the
conjugate acid, and chloride ion (Cl-), the conjugate base.

13. Acid-Base Property of
Water
•A compound like water, H2O,
that contains both a hydrogen
atom and a lone pair of
electrons can act as an acid or a
base, depending on the specific
reaction. Compound exhibiting
such property is called
amphoteric.

14. H2O acts as an acid -When water acts as an acid, it
will donate proton to the base.

15. H2O acts as a base- When water acts as a
base, it will accept proton.

16. •Water can also
undergo self-
ionization or auto-
ionization, the
process occurs
when water
molecules react
with another
molecule to form
H3O+ and OH-.

17. Self-ionization
•The reaction in which a water
molecule donates one of its
protons to a neighboring water
molecule (both base and acid/
amphoteric)

18. Autoionization
•In autoionization of water,
a proton is transferred
from one water molecule
to another to produce
hydronium ion (𝐻3𝑂+
)and
a hydroxide ion (𝑂𝐻−
)

19. Practice Exercise 1. Label each reactant as A1 for Bronsted-Lowry acid or B1 for
Bronsted-Lowry base and each product as CA, for conjugate acid or CB for conjugate
base. Then, write the conjugate acid-base pair.