Acid Rain

1
Acid Rain

• Saying sulfates do not cause acid rain is the
  same as saying that smoking does not cause lung
  cancer. -Drew Lewis- American Secretary of
  Transportation, 1981-83
• Police arrested two kids yesterday, one was
  drinking battery acid, the other was eating
  fireworks. They charged one and let the other one
  off. -Tommy Cooper-

2
Quiz

• Please List two characteristics of acids.
• Please List two characteristics of bases.
• Please Write out the chemical reaction that shows
  ammonia NH3 acting as a base.

3

• Please List two characteristics of acids.
• Sour, turn litmus Red release H in water,
  proton donor
• Please List two characteristics of bases.
• Bitter, Turns litmus blue, releases OH in water,
  proton acceptor, slippery
• Please Write out the chemical reaction that shows
  ammonia NH3 acting as a base.
• NH3 H2O NH4 -OH
• Question that Dr Freeman could have asked and
  might at a later date. Please define
  Equilibrium.

4
Where We Are

• Completed Section 6.2
• should complete 6.5 -6.6 today
• Problems to try in addition to those in the text
• 1-12, 24, Concept problems 26-36 Extensions
  40-51
• Papers due Today
• Volunteers wanted for presentations on Monday
  April 28. Group leaders MUST contact me by
  Friday April 18th To Schedule your presentation

5
When acids and bases react with each other, we
call this a neutralization reaction.
HCl(aq) NaOH(aq) NaCl(aq)
H2O(l) In neutralization reactions, hydrogen
ions from an acid combine with the hydroxide ions
from a base to form molecules of water. The
other product is a salt (an ionic compound).
6.3
6
Consider the reaction of hydrobromic acid with
barium hydroxide
This reaction may be represented with a
molecular, ionic, or net ionic equation Molecular

2 HBr(aq) Ba(OH)2(aq)
BaBr2(aq) 2 H2O(l) Ionic 2 H(aq)
2 Br(aq) Ba2(aq) 2 OH(aq)
Ba2(aq) 2 Br(aq) 2 H2O(l) Net
Ionic 2 H(aq) 2 OH(aq) 2
H2O(l) or by dividing both sides of the
equation by 2 to simplify it H(aq)
OH(aq) H2O(l)
6.3
7
2 HBr(aq) Ba(OH)2(aq) BaBr2(aq)
2 H2O(l)
How did we go from Ionic to Net Ionic?
Ionic 2 H(aq) 2 Br(aq) Ba2(aq) 2
OH(aq) Ba2(aq) 2 Br(aq)
2H2O(l) Remove the species that
appear unchanged on both sides of the reaction
- these are called spectator ions
6.3
8
2 HBr(aq) Ba(OH)2(aq) BaBr2(aq)
2 H2O(l)
How did we go from Ionic to Net Ionic?
Ionic 2 H(aq) 2 Br(aq) Ba2(aq) 2
OH(aq) Ba2(aq) 2 Br(aq) 2
H2O(l)
6.3
9
Balance the following equations, then write the
ionic equations and net ionic equations for the
following.
H2SO4 NaOH ? H3PO4 Mg(OH)2 ?
10
From Monday 0ne in 550,000,000 water molecules
is broken apart in water at any on time.
2H2O H30 -OH We can express this
relationship mathematically as follows K eq
Products /Reactants In this case Keq
H3OOH/H2O
For an extra quiz show this is true. ask me I can
help
Because in water H2O is essentially constant at
55 Molar we can express this as Kw the
ion-product constant for water. Kw H-OH
In pure water the concentration of H and OH
are 10-7 So Kw H-OH 10-7 10-7 1 x
10-14 (at 25 oC)
6.4
11
To measure the pH in aqueous solutions, we make
use of the expression Kw HOH- 1 x
10-14 (at 25 oC) where Kw is the ion-product
constant for water. Knowing the hydroxide ion
concentration, we can calculate the H, and use
the pH expression to solve for pH. Knowing the
H we can know OH as well
The three possible aqueous solution situations
are H OH- a neutral solution (pH
7) H OH- an acidic solution (pH 7) H 7)
6.4
12
The pH of a solution is a measure of the
concentration of the H ions present in that
solution. The mathematical expression for pH is
a log-based scale and is represented as
pH -log H
So for a solution with a H 1.0 x 10-3 M,
the pH -log (1.0 x 10-3), or -(-3.0) 3.0
Since pH is a log scale based on 10, a pH change
of 1 unit represents a power of 10 change in
H. That is, a solution with a pH of 2 has a
H ten times that of a solution with a pH of 3.

6.4