Transcript Slide 1

Warmup
Solve for x:
1) If the pH is 4, what’s the [OH]?
2) logx 256 = 4
3) 10x = .000015
4) Write a chemical equation for the disassociation of the Bronstead-Lowry
base, ammonia (NH3) in water.
Then setup the expression through which you’d calculate its
disassociation constant.
FEBRUARY 28, 2011
References:
http://library.thinkquest.org/C006669/data/Chem/equilibrium/ka.html
http://www.chembuddy.com/?left=BATE&right=dissociation_constants
Partial Disassociation
Remember: the items in
brackets are Molarities.
Take the Molarity of the salt\
acid\ base concentration, and
plug it in like so:
Ka = x * x / (Total – x) where
solving for x will help you find
the total dissolved.
Bases
Disassociation Constants List
Acids
Bases
acetic (ethanoic) acid CH3COOH
4.75
ammonia
NH3
4.75
citric acid
3.13
calcium hydroxide
Ca(OH)2
2.43
C6H8O7
4.76
6.40
carbonic acid
H2CO3
6.37
10.25
1.4
lithium hydroxide
LiOH
-0.36
methylamine
CH3NH2
3.36
hydrochloric acid
HCl
-4
ethylamine
C2H5NH2N
3.25
hydrogen sulfide
H2S
7.04
potassium hydroxide
KOH
0.5
11.96
sodium hydroxide
NaOH
0.2
aniline
C6H5NH2
9.4
*
nitric acid
HNO3
-1
oxalic acid
(COOH)2
1.25
4.27
*
perchloric acid
HClO4
-7
phenol
C6H5OH
9.89
phosphoric acid
H3PO4
2.15
7.20
12.35
*
sulphuric acid
H2SO4
-3
1.99
The values listed are pKa’s, not Ka’s.
10^-pKa = Ka
Sample Problem 5
What is the pH of a 0.10 M H2SO4 solution (pKa = -3, 1.99)?