Transcript Our Next Lab

Our Next Lab
Our Next Lab
Determining
Hydrogen Ion Concentration
of Strong and Weak Acids.
Our Next Lab
HCl →
+
H
+
Cl
Our Next Lab
HCl →
+
H
+
Cl
This is a strong acid
Our Next Lab
HCl →
+
H
+
Cl
This is a strong acid
It dissociates completely.
Our Next Lab
HCl →
+
H
+
Cl
If one mole of HCl is dissolved
in one liter of solution, then
+
[H ] = 1 M
Our Next Lab
HCl →
+
H
+
Cl
If one mole of HCl is dissolved
in one liter of solution, then
+
0
[H ] = 1 x 10 M
pH = 0
Our Next Lab
HC2H3O2 ↔
+
H
+ C2H3O2
-
Our Next Lab
HC2H3O2 ↔
+
H
+ C2H3O2
This is a weak acid
-
Our Next Lab
HC2H3O2 ↔
+
H
+ C2H3O2
-
This is a weak acid
It does not dissociate completely.
Our Next Lab
HC2H3O2 ↔
+
[H ]
+
H
+ C2H3O2
[C2H3O2 ]
+
Ka = -------------------------[HC2H3O2]
-
Our Next Lab
Your challenge, in today’s lab,
is to experimentally determine
Ka for HC2H3O2.
Safety:
Goggles
Gloves
Aprons.
Groups:
•Work in groups of three or four
•One person in each group is the
“manager.” the manager’s job is
to keep track of directions
•Read the directions carefully
•Questions? Go to your manager
first.
Grades:
•Separate grades for activity and
for write-up.
Step 1:
Label 12 test tubes:
Set 1:
0.1 M HCl
0.01 M HCl
0.001 M HCl
0.0001 M HCl
unknown
acetic acid
Set 2:
0.1 M HCl
0.01 M HCl
0.001 M HCl
0.0001 M HCl
unknown
acetic acid.
Step 2:
Follow written directions to
mix up solutions.
Step 3:
•Add one drop of methyl
orange indicator to each
solution in set 1.
•Add 1 drop of orange IV
indicator to each solution
in set 2.
Data:
The four different concentrations
of HCl are your standard.
Compare your unknown acid and
your acetic acid to your standard
solutions.
Record your observations.
Conclusions:
+
The color will tell you the [H ].
The [H+] will tell you the pH.
It will also let you calculate Ka.
Answer the “Conclusions and
Questions” at the end of your
packet.
12 test tubes:
Set 1:
0.1 M HCl
0.01 M HCl
0.001 M HCl
0.0001 M HCl
HCl
unknown
acetic acid
Set 2:
0.1 M HCl
0.01 M HCl
0.001 M HCl
0.0001 M
unknown
acetic acid.