Acids, Bases, and Salts,
Part II
Characteristics
of an Acid
1.
Taste Sour
2.
Undergo Protolysis –
the splitting of protons from the molecule (-lysis means “to split away from”)
a.
Remember through Protolysis, a
molecule is losing a Proton which is the same as a H+ ion
3.
Corrosive – eat through material’s through protolysis
4.
The strength of an acid is dependant
upon how completely it ionizes in water
a.
Strong acids ionize completely
producing excess H30+ ions
i. H+ + H2O -> H3O+
5.
Common Acids:
a.
HCl – Hydrochloric Acid
b.
H2SO4 –
Sulfuric Acid
Characteristics
of a Base
1.
Taste Bitter
2.
Slippery
3.
Strength of base (same as acid
except will produce OH- ions in water)
4.
Caustic- eat through materials through OH production
5.
Common Bases:
a.
Ca2OH – Tums
b.
NHOH – Windex
c.
NaOH – Lye
Indicators
– Changes color in the presence of an Acid or a Base
1.
Litmus Paper
a.
Acid = Red
b.
Base = Blue
2.
Phenolphthalein
a.
Base = Red
b.
Acid = Colorless (no change)
3.
Bromthymol Blue (BTB)
a.
Base = Blue
b.
Acid = Yellow
4.
Universal Indicator
a.
Base = Green/Purple (“Bleych”)
b.
Acid = Red
5.
Methyl Orange
a.
Acid = Red
b.
Base = Yellow
Neutralization
Reactions – “Salt Producing”
1.
Acid + Base -> Salt + Water
a.
HCl + NaOH -> NaCl + H2O
2.
Acid + Base Anhydride ->
Salt + Water
a.
K2O + 2HCl ->
2KCl + H2O
3.
Acid Anhydride + Base ->
Salt + Water
a.
SO3 + 2NaOH ->
Na2SO4 + H2O
i. Remember to Hydrate the Anhydride (SO3 + H2O ->
H2SO4)
4.
Acid Anhydride + Base Anhydride
-> Salt
a.
SO3 + Na2O
-> Na2SO4
5.
Acid + Metal -> Salt +
Hydrogen Gas
a.
HCl + Ag -> AgCl + H+
( indicates that the product is released as a gas)
6.
Acid + Carbonate -> Salt
+ Water + Carbon Dioxide
a.
2HCl + CaCO3 ->
CaCl2 + H2O + CO2
7.
Metal + Nonmetal -> Salt
a.
2K + Cl2 ->
2KCl
8.
Salt(aq) + Salt(aq) ->
Salt + Salt (Double Replacement)
a.
NaBr + KCl -> NaCl + KBr
i. Remember one must consider each element’s Electronegativity
in order to determine whether a reaction will occur. (Ionic bonds occur in elements
that differ in EN greater than 1.67)
Parent
Acids and Parent Bases
When given a salt, one
can find the parent acid by taking the back half of the acidic product and the front half of the basic product. Thus, we can write the Neutralization Reaction between the two parents to obtain the salt.
Ex:
Salt: NaCl
Parent Acid: H++
Cl -> HCl
Parent Base: Na + OH- -> NaOH
Neutralization rxn: HCl + NaOH -> NaCl + H2O
Salt: LiNO3
Parent Acid: H+
+ NO3 -> HNO3
Parent Base: Li + OH- -> LiOH
Neutralization rxn: HNO3 + LiOH -> LiNO3 + H2O
Determining
the strength of Acids and Bases
An Acid or Bases strength
is defined by how completely it ionizes in water. A Strong Acid/Base will
ionize completely into H+ and OH- ions. In a Weak
Acid/Base, not all molecules will dissociate/ionize.
Acids
are strong when:
1.
It is Binary (Composed of 2 elements)
a.
HCl
b.
HF
c.
H2S
2.
In Ternary compounds (Composed
of 3 elements), the compound must have 2 more Oxygen atoms than Hydrogen atoms
a.
H2SO4 (4O
– 2H ³ 2)
b.
H3PO5 (5o
– 3H ³ 2)
i. Most “Per-stemic Acids” are strong
Acids
that are not strong are considered Weak
Bases
are strong when:
1.
The stem element belongs to group
IA
a.
KOH
b.
NaOH
2.
The stem element belongs to group
IIA
a.
Ca(OH)2
b.
Be(OH)2
Hydrolysis
– Rxn of Salt and Water
Salt produced from a Strong
Acid and a Strong Base -> Neutral Solution
Salt produced from a Weak
Acid and a Strong Base -> Basic Solution
Salt produced form a Strong
Acid and a Weak Base -> Acidic Solution
Salt produced from a Weak
Acid and a Weak Base -> Dependant on which reactant dissociates more.
Salt
Parent Acid Strength Parent Base
Strength Solution Type
NaCl
HCl
Strong
NaOH
Strong
Neutral
FeNO3
HNO3
Strong
FeOH
Weak
Acidic
Mg3(PO2)2 H3PO2
Weak
Mg(OH)2 Strong
Basic
CuSO3
H2SO3
Weak
Cu(OH)2
Weak
Unknown
pH
and pOH
“[ ]” denotes Concentration (Molarity – mole/1L)
pH = -log[H+]
pOH = -log[OH-]
pH
is the measure of the concentration of H3O+ ions in a solution.
pOH
is the measure of the concentration of OH- ions in a solution.
A
solution’s pH and pOH will add to 14
The pH of HCl is 2. The pOH can be found by subtracting 2 from 14.
14 – 2 = 12
The pOH of HCl is 12
Water
is Amphoteric (can act as an Acid or a Base)
2H2O -> H3O+
+ OH- (Remember: H+
+ H2O -> H3O+)
In
pure water, the Acidic part (H3O+) and the Basic part (OH-) are in perfect balance, thus
forming a neutral solution.
If
[H3O+] > [OH-] then the solution is an Acid
If
[H3O+] < [OH-] then the solution is a Base
If
[H3O+] = [OH-] then the solution is Neutral
In
pure water, [H3O+] = [OH-] = 1.00 x 10-7 M
pH
= 7 pOH = 7
-log(10-7)
+ -log(10-7)
-(-7)
+ -(-7) = 14
Equilibrium
Constant (Concentration of ions at equilibrium)
(Keq)
= [product 1][product 2][product 3]… Divided by [reactant 1][reactant2]…
aA
+ bB -> cC + dD (where A and B are Reactants, C and D are Products and a, b, c, and d are Coefficients)
Keq
= [C]c + [D]d divided by [A]a + [B]b
Keq
of water (Kw)
2H2O -> H3O + OH
( [H3O] [OH]
)/ [H2O]2 = Kw
( 1.00 x 10-7
)( 1.00 x 10-7 )/12 = 1.00 x 10-14 = Kw
pH 0 ßà7ßà14
0-7
= Acid
7
= Neutral
7-14
= Base
pOH 0 ßà7ßà14
0-7
= Base
7
= Neutral
7-14
= Acid
Finding
pH and pOH from a given concentration
If
[H3O+] = 1.00 x 10-5 M find pH, pOH, [OH-]
1.00 x 10-14
= [H3O+][OH-]
1.00 x 10-14
= 1.00 x 10-5 [OH-]
1.00 x 10-9
= [OH-]
pH = -log(1.00 x 10-5)
pH = 5
pOH = -log(1.00 x 10-9)
pOH = 9
Solution is Acidic
