you enter for your sample calculation should exactly match the corresponding values you entered
above.)
Enter a sample calculation for the equilibrium constant,
K
eq
, based on sample 2 in Part 4. (The
values you enter for your sample calculation should exactly match the corresponding values you
entered above.)
A
=
−
log
=
−
log
=
0.302
0.302
%
T
100%
49.9
49.9
%
100%
M
=
=
=
4.1e-5
4.1e-05
mol/L
−
log
(
ε
)(
b
)
T
%
100%
−
log
3800
3800
L/mol
·
cm
1.00
1.00
cm
70.0
70.0
%
100%
K
eq
=
=
=
260
260
[FeSCN
2+
]
[Fe
3+
] [SCN
−
]
4.0e-5
4.0e-05
9.6e-4
0.00096
1.6e-4
0.00016
Discuss what you found out and how.

product favored, while the test tube in the beaker of ice had a dark red-orange color, showing that
the reaction was exothermic and reactant favored.
For part 2, the wavelength of minimum Transmittance percentage and maximum absorbance was
determined through analysis of the spectroscopic data collected through the Spec 20 machine. The
wavelength that presented the most absorbance and minimum Transmittance was at 440
nanometers as it presents 0.614 absorbance.
For part 3, the slope of Beer's law was determined by adding different amounts of NaSCN into a
solution of Fe^3+ and the percent of transmittance was calculated for each sample. Each sample
has a different increasing amount of NaSCN added into the solution, and the slope of
transmittance against concentration of the solution was 3800 M^-1*cm^-1.
For part 4, the K equilibrium value was determined by calculating the percent of transmittance as
each sample receives an increasing amount of NaSCN. The K equilibrium value was calculated to
be 305 with a standard deviation of 28, where there is also a 31 out of 36 ratio of FeSCN in
concentration.
Key:
Answers will vary.
Score:
5 out of 5
Comment:
Graded: 5 points by Tambo TA, Carrie on Saturday, May 27 2017 04:27 PM PDT.
Relate results to predictions/theory.
This lab goes to show that assumptions are bad for analyzing data as the percent error could
increase with each assumption. In part 4, where the assumption was made that the K equilibrium
value was 310 and when calculated that the concentration of the Fe^3+ could be determined from
that value, which was 31, and that also led to a larger percent in error.
Key:
Answers will vary.
Score:
5 out of 5
Comment:
Graded: 5 points by Tambo TA, Carrie on Saturday, May 27 2017 04:27 PM PDT.
How was Part 3 dependent on Part 2?
Part 2 was to gauge the wavelength that provided the largest absorbance and lowest
transmittance value, and that data would be used to determine absorbance of each sample in part
3.