Concentration vs' Strength

1
Concentration vs. Strength
Concentrated vs. Dilute
Strong vs. Weak
2
Acids Concentration vs. Strength
DILUTE
CONCENTRATED
H A - H A - HA A -
H A - H A H A -
H A - H A - HA H
A - H A - H A - H
H A- H A- H A- H A- HA A- H A-
H A- H A- H A - H A- HA H A- H
A- H A- A- H A- H A- H A- H A-
H H A - H A - H A - HA H A - A- H
A- H A- H A- H A H A- H A- H
A- H A- H A- H A- H A- H A-
H A- HA A- H A- H A- H A- H
STRONG ACIDS Dissociate nearly 100
HA H1 A- WEAK
ACIDS Dissociate very little HA
H1 A-
STRONG
HA HA HA HA HA HA
HA H A - HA HA HA
HA H A HA H A HA HA
HA HA H A- HA HA HA HA HA
HA HA HA H A- H A- HA HA
HA HA HA HA HA H A- HA HA
HA HA HA HA H A- HA HA
H A- HA HA HA HA HA HA
HA HA H A- HA HA H A- HA
HA HA HA HA HA HA H A-
HA HA HA
WEAK
3
Comparison of Strong and Weak Acids
Reversibility of reaction
Ions existing when acid, HA, dissociates in H2O
Type of acid, HA
Ka value
Not reversible
H and A-, only. No HA present.
Ka value very large
Strong
Weak
reversible
Ka is small
H, A-, and HA
HA(aq) H2O(l) H3O(aq)
A-(aq)
The equilibrium expression for the reaction is
H3O A-
Note H3O H
Ka
HA
4
Strong vs. Weak Acid
Zumdahl, Zumdahl, DeCoste, World of Chemistry
2002, page 508
5
Concentrated vs. Dilute
0.3 M HCl
10.0 M CH3COOH
Dilute, strong acid
Concentrated, weak acid
2.0 M HCl
Concentrated, strong acid
OR Dilute, strong, acid
12.0 M HCl
Concentrated, strong acid
6
Naming Acids
Anion
Acid
_________ ide (chloride, Cl1-)
Hydro____ ic acid (hydrochloric acid, HCl)
add H
ions
_________ic acid (chloric acid,
HClO3) (perchloric acid, HClO4)
_________ ate (chlorate, ClO3-) (perchlorate,
ClO4-)
add H
ions
_________ite (chlorite, ClO2-) (hypochlorite,
ClO-)
______ous acid (chlorous acid, HClO2) (hypochlorou
s acid, HClO)
add H
ions
7
Increasing acid Strength
Increasing base Strength
Increasing acid Strength
Increasing base Strength
Brown, LeMay, Bursten, Chemistry 2000, page 625
8
Equilibrium and pH Calculations
Weak acid
Strong acid
HA H2O H3O A-
HA H2O H3O A-
acid-dissociation constant calculations
HA H3O
H3O

antilog(-pH)
OH-
-log H3O
pH
-
0 7 14
Tocci, Viehland, Holt Chemistry Visualizing
Matter 1996, page 525