Download H 3 O + - St John Brebeuf

Acids and Bases
Lesson 1
Acid & Base Properties
(Strong & Weak acids)
Properties of Bases
Neutralize acids
Are electrolytes that conduct electricity
Change litmus paper blue
Feel slippery
Taste bitter (baking soda)
Ex: NaOH, Ca(OH)2, KOH, Zn(OH)2
-- notice they all contain OH.
Properties of Acids
Neutralize bases
Are electrolytes that conduct electricity
Change litmus paper red
Taste sour (vinegar, lemon juice)
React with metals such as Mg and Zn to make H2
Mg(s)+ 2 HCl (aq)  MgCl2 (aq) + H2(g).
Ex: HCl, HNO3, H2SO4 –notice they all contain H.
Salts
A salt is the neutralization product when
an acid and a base react to produce
water.
HCl + NaOH  NaCl + H2O
Notice, a salt does not contain H, or OH.
The Arrhenius Theory of
Acids and Bases
produces H+ in solution
Arrhenius acid
HCl

H+
+
ClH+ is called a
proton
produces OH- in solution
Arrhenius base
NaOH

Na+ + OH-
Bronsted-Lowry Theory of
Acids and Bases
Bronsted-Lowry Theory of
Acids and Bases
-more general theory
-to accommodate reactions at equilibrium.
-acids as proton donors
-bases as proton acceptors
Bronsted Acid
Chemistry 12
A proton donor
H+
HCl
+
H2O

H3 O+
+
Cl-
strong
Bronsted Base
NH3
A proton acceptor
Chemistry 12
+
H+
H2O
⇄
weak
NH4+
+
OH-
Write a Bronsted reaction for the weak base HCO3-
H+
HCO3-
+
base
HCO3- and H2CO3
H+
H2 O
acid
⇄
H2CO3
acid
H2O and OH-
These are called “Conjugate acid-base pairs”
They differ by one proton H+
+
OHbase
In Summary
1.
Arrhenius bases dissociate in water to produce OH-
2.
Bronsted bases accept a proton from water to produce OH-
3.
Arrhenius acids dissociate in water to form H+
4.
Bronsted acids donate a proton to water to form H3O+
5.
H+ is the same as H3O+
H+ is another way to show H3O+.
H+
+
H2 O
⇋
Hydronium ion
Proton
+
H+
H2 O
H3 O +
Conjugate acids and
bases
Conjugates
A conjugate acid-base pair (conjugate pair) is a pair of
chemical species which differ by only one proton (H+)
NH4+, NH3
A conjugate acid is the member of conjugate pair that HAS the
extra proton.
NH4+
A conjugate base is the member of the conjugate pair that
LACKS the extra proton.
NH3
Conjugate Acid
One more H+
Conjugate Base
1 less H+
C6H5OH
C 6 H 5 O-
H2CO3
HCO3-
H2 O
OH-
HPO42-
PO43-
H2PO4-
HPO42-
C6H5COOH
C6H5COO-
NH4+
NH3
Fe(H2O)63+
Fe(H2O)5(OH)2+
H+ gives a
+1
Charge.
Acids and Bases Chart p334
Relative Strengths of Bronsted-Lowry Acids
and Bases
Aqueous solutions at room temperature.
Strong Acids
Weak Acids
Strong Acids
Left side of Acid Chart -top sixCompletely ionize in water
Are good conductors.
Produce large amounts of H3O+.
Have very large Ka’s, that is why you do not find them on the chart.
Use a “” and not “⇄” because it is not an equilibrium situation.
HCl + H2O  H3O+
+
Cl-
Weak Acids
Left side of the Acid Chart below the top six.
Do not completely ionize in water.
Are poor conductors.
Produce small amounts of H3O+.
Have small Ka’s, you will find Ka values on the chart.
Use a “⇄” and not “” It means they are Equilibrium situations!
HF + H2O ⇄ H3O+
+
F-
[H3O+][F-]
=
3.5 x 10-4
from page 334
[HF]
Water is not included because it is a pure liquid! Its concentration is constant!
Ka
=
You can also write:
HF + H2O ⇄ H3O+
+
HF + H2O ⇌ H+
+
FF-
[H+][F-]
Ka =
=
3.5 x 10-4
[HF]
We use H+ and H3O+
interchangeably. They mean the
same thing!
Balance these neutralization equations
H2SO4 + NaOH
HCl + Sn(OH)4
Homework:
Hebden: Pg 110 #1-2, Pg. 112 #3-4