Question

In lab data:

Trial	Fe(No3)3 mL	KSCN mL	H2O ML	Total Vol. mL	%T
1	5.00	5.00	0	10.00	13.2
2	5.00	4.00	1.00	10.00	18.4
3	5.00	3.00	2.00	10.00	24.2
4	5.00	2.00	3.00	10.00	43.4

trial	%Transmittance	Absorption	[FeSCN] 2+
1	13.2	?	?
2	18.4
3	24.2
4	43.4

How do you calculate Absorption?

Conc. Fe(NO3)3 solution used ? Conc. KSCN solution used ?

Answer 1

Absoption or absorbance (A) = -LogT

In trial 1, %T = 13.2, i.e. T = 13.2/100 = 0.132

Now, A = -Log(0.132) = 0.879

In trial 2, %T = 18.4, i.e. T = 18.4/100 = 0.184

Now, A = -Log(0.184) = 0.735

In trial 3, %T = 24.2, i.e. T = 24.2/100 = 0.242

Now, A = -Log(0.242) = 0.616

In trial 4, %T = 43.4, i.e. T = 43.4/100 = 0.434

Now, A = -Log(0.434) = 0.362

Formula: A = cl

Where, is the molar extinction coefficient which is specific for the absorbing complex or medium at a given wave length, c is the conentration of absorbing medium, here it is FeSCN²⁺ and l is path length.

You can find value from the internet and l value from the experimentalist, who is recording the data, A value is already calculated.

Now, by using all these values, you can calculate the c value.

All the best!