Msc zoology fourth semester Acids and Bases.ppt

Science notes

1. Acids
and
Bases
Chemistry Chapter 15
Acids and BasesAcids and Bases

2. Acids
and
Bases
Some Definitions
•Arrhenius acids and bases
Acid: Substance that, when dissolved in
water, increases the concentration of
hydrogen/hydronium ions (protons, H
+
or

H
3O
+
).
Base: Substance that, when dissolved in
water, increases the concentration of hydroxide
ions.

3. Acids
and
Bases
Some Definitions
•Brønsted–Lowry: must have both
1. an Acid:Proton donor
and
2. a Base:Proton acceptor

4. Acids
and
Bases
The Brønsted-Lowry acid donates a proton,
while the Brønsted-Lowry base accepts it.
Brønsted-Lowry acids and bases are always paired.
Which is the acid and which is the base in each of these rxns?

5. Acids
and
Bases
What Happens When an Acid
Dissolves in Water?
•Water acts as a
Brønsted–Lowry base
and abstracts a proton
(H
+
) from the acid.
•As a result, a
hydronium ion (H
3
O
+
)
is formed.

6. Acids
and
Bases
Ionization of HCl and formation of
hydronium ion, H
3O
+
H
2O + HCl  H
3O
+
+ Cl
-
Proton
donor
Proton
acceptor

7. Acids
and
Bases
A Brønsted–Lowry acid…
…must have a removable (acidic) proton.
HCl, H
2O, H
2SO
4
A Brønsted–Lowry base…
…must have a pair of nonbonding electrons.
NH
3, H
2O

8. Acids
and
Bases
Salts
•Compounds that dissociate releasing
neither H
+
or OH
-
ions
•Example:
KCl  K
+
+ Cl
-

9. Acids
and
Bases
Properties of Acids
 Acids taste sour
 Acids affect indicators
 Blue litmus turns red
 Methyl orange turns red
 Acids have a pH lower than 7
 Acids are proton (hydrogen ion, H
+
) donors
 Acids react with active metals, produce H
2

Acids are electrolytes
 Acids neutralize bases to produce a salt
and water

10. Acids
and
Bases
Acids change Indicators
Blue litmus paper turns red in contact
with an acid.

11. Acids
and
Bases
Acids React with Active
Metals
Acids react with active metals to form
salts and hydrogen gas.
Mg + 2HCl  MgCl
2
+ H
2
(g)

12. Acids
and
Bases
Acids Neutralize Bases
HCl + NaOH  NaCl + H
2
O
Neutralization reactions ALWAYS
produce a salt and water.

13. Acids
and
Bases
Acids are Proton Donors
Monoprotic acidsDiprotic acidsTriprotic acids
HCl
HC
2H
3O
2
HNO
3
H
2
SO
4
H
2CO
3
H
3PO
4

14. Acids
and
Bases
Uses
•H
3
PO
4
- soft drinks, fertilizer, detergents
•H
2SO
4 - fertilizer, car batteries
•HCl - gastric juice
•HC
2
H
3
O
2
- vinegar

15. Acids
and
Bases
Acids you must know:
Strong Acids Weak Acids
Hydrochloric acid, HCl
Nitric acid, HNO
3
Sulfuric acid, H
2SO
4 Phosphoric acid, H
3PO
4
Acetic acid, HC
2
H
3
O
2
Hydrobromic acid, HBr
Hydroiodic acid, HI
Perchloric acid, HClO
4

16. Acids
and
Bases
Properties of Bases
 Bases taste bitter
 Bases affect indicators
 Red litmus turns blue
 Phenolphthalein turns purple
 Bases have a pH greater than 7
 Bases are proton (hydrogen ion, H
+
) acceptors
 Solutions of bases feel slippery
 Bases neutralize acids to produce a salt and
water

17. Acids
and
Bases
Examples of Bases
 Sodium hydroxide (lye), NaOH
 Potassium hydroxide, KOH
 Magnesium hydroxide, Mg(OH)
2
 Calcium hydroxide (lime), Ca(OH)
2

18. Acids
and
Bases
Uses
•NaOH - lye, drain and oven cleaner
•Mg(OH)
2 - laxative, antacid
•NH
3 - cleaners, fertilizer

19. Acids
and
Bases
Naming Acids, Bases, Salts
•Bases & Salts- Ionic
Name the same as ionic compounds
•Acids
Binary
•2 elements, first hydrogen
•Hydro___ic acid
Ternary
•3 elements, change ending
•-ate  ic, -ite  ous

20. Acids
and
Bases
Strong Acids vs. Weak Acids
Strong acids are assumed to be 100%
ionized in solution (good proton donors).
Weak acids are usually less than 5%
ionized in solution (poor proton donors).
HCl H
2SO
4 HNO
3
H
3PO
4HC
2H
3O
2Organic acids

21. Acids
and
Bases
Strong Acid Dissociation

22. Acids
and
Bases
Weak Acid Dissociation

23. Acids
and
Bases
•Which of the following "molecular" pictures
best represents a concentrated solution of
the weak acid HA?
Concept Test
A B

24. Acids
and
Bases
pH Scale
0

7
INCREASING
ACIDITY
NEUTRAL
INCREASING
BASICITY
14
•pHpH
a measure of the concentration of H
3
O
+
ions in
solution
measured with a pH meter or an indicator with
a wide color range

25. Acids
and
Bases
Acids
Have a
pH less
than 7

26. Acids
and
Bases
Bases
have a pH
greater
than 7

27. Acids
and
Bases
pH Scale
pH of Common SubstancespH of Common Substances

28. Acids
and
Bases
ACID + BASE ACID + BASE  SALT + WATER SALT + WATER
HCl + NaOH HCl + NaOH  NaCl + H NaCl + H
22OO
Neutralization does not always mean pH = 7.
=
Neutralization Reaction

29. Acids
and
Bases
KOH + HNO
3  H
2O + KNO
3
Acid?
Base?
Salt?
HNO
3
KOH
KNO
3
Neutralization Reaction

30. Acids
and
Bases
Products of Neutralization
HCl + NaOH 
H
2
SO
4
+ Ca(OH)
2

HNO
3
+ KOH 
The products of neutralization are always
a ______ and _______.
NaCl + H
2O
CaSO
4
+ 2 H
2
O
KNO
3
+ H
2
O
salt water