Question

Experimental Volumes
Mixture		Volume (mL) Fe(NO3)3		Assigned Volume (mL) KSCN Read Instructions Above		Volume (mL) KSCN Read Instructions Above		Volume (mL) Water
You (Blank)		5.00		0.00		0.00		5.00
You (Volume 1)		5.00		0.5		Read Instructions Above!! 0.7		Try 1: ✔ 4.30 1 1
You (Volume 2)		5.00		2.2		2.2		Try 1: ✔ 2.80 1 1
You (Volume 2 Chilled)		5.00		2.2		2.2		2.80
Partner (Blank)		5.00		0.00		0.00		5.00
Partner (Volume 1)		5.00		3.2		3.9		Try 1: ✔ 1.10 1 1
Partner (Volume 2)		5.00		4.5		4.8		Try 1: ✔ 0.20 1 1

Spectrometer Readings
Mixture		%T (1st Reading)		%T (2nd Reading)		Average %T		Absorbance
You (Blank)		96.9		98.7		Try 1: ✔ 97.8 1 1		0.00
You (Volume 1)		34.7		34.5		Try 1: ✔ 34.6 1 1		NG 1
You (Volume 2)		29.2		29.4		NG 1		NG 1
You (Volume 2 Chilled)		53.2		42.7		NG 1		NG 1
Partner (Blank)		92.6		92.1		NG 1		0.00
Partner (Volume 1)		83.5		83.7		NG 1		NG 1
Partner (Volume 2)		56.7		57.5		NG 1		NG 1

How do i get absorbance ?

Answer 1

We know that

%T = I/Io * 100

we know  T = I/I_o

so, T = %T / 100 .............(1)

and also we know

A = -log T .................(2)

Now putting the value of T from equation (1) in equation (2), we get;

A = -log (%T / 100) .......................(3)

Now putting the value of %T in equation (3), we get

for blank we have

A = -log(97.8/100)

= log(100/97.8)

= 0.00

for volume 1, we have

A = -log(34.6/100)

= log(100/34.6) = 0.46

for volume 2, we have %T average = (29.2+29.4)/2 =29.3

A = -log(29.3/100)

= log(100/29.3) = 0.53

similarly we can calculate Absorbance for each %T reading.

hope this helps!

NOTE: A = absrobance

T = transmittance

%T = %transmittance

I = intensity of the light transmitted

Io = intensity of the light entering