4.
Write the equation for the linear fit line from your graph in the form
y
=
mx
+
b
, using the
values for
m
and
b
that you recorded in the Evidence Record. For example, if
m
= 3 and
b
= 6,
then the equation for the line is
y
= 3
x
+ 6.
Y = 6.049x + 0.001355
5.
The accuracy of your standard concentrations is indicated by the correlation coefficient (also
known as the
r
value). Report your
r
value.
R: 0.9982
6.
Show how to use the equation of the line and the measured absorbance of an unknown to
find the concentration of FeSCN
2+
as follows:
a.
In the equation for the line of best on the calibration graph, which physical quantity is
represented by
y
and which physical quantity is represented by
x
?
Y represents absorbance and X represents concentration in m/L.
b.
Rewrite the equation so that you have a formula to find concentration from absorbance
(isolate concentration on one side of the equation).
X = (Y - 0.001355) / 6.049
c.
Choose one of the unknowns you measured and substitute the measured quantities for
the unknown into your formula to confirm that the concentration recorded from the
interpolation calculator in Logger Pro agrees with the concentration you calculate using
your formula.
