Question

Fe 2+ Concentration	Measured Absorbance
0.399	0.080
0.799	0.164
0.999	0.201
1.998	0.405
3.996	0.805

Using the above data for a standard curve, how can I determine the Concentration of iron (Fe+2) in Solution 3 and Solution 1? How can I also determine the average mass of iron in the tablet?

C2(?) x V2(5.00mL) = C3(from standard curve) x V3(50.0 mL)

C1(?) x V1 (5.00mL) = C2 x V2 (100.0 mL)

Tablet Name:  ShopRite Iron (C)                   Mass (on label): 65 mg

	Trial 1	Trial 2
Measured Absorbance (Solution 3)	0.633	0.626
Concentration of iron (Fe+2) in Solution 3	?	?
Concentration of iron (Fe+2) in Solution 1	?	?
Mass of iron in tablet	?	?

Average mass of iron in tablet	? mg
Relative Error (compared to mass on label)	?

Answer 1

Solution:-

=> First you have to draw standard curve by taking concentration on x-axis and measured absorbance on y-axis as concentration absorbance, you get a straight line.

=> you didn't give units for Fe+2 concentration, I think the concentrations are in ug / ml (units of concentration of Fe+2 are very important)

The equation of line i got is

Y = 0.2013x + 0.0012

y = absorbance, X = concentration value

For solution 3:-

We have absorbance value = 0.633

substitute this value in equation

0.633 = 0.2013x + 0.0012

x = concentration = 3.14 ug / ml