The absorbance of a standard solution of 2.032 times 10^-4 M FeSCN^+2 (aq) was determined to be 1.086. A student prepared a solution containing 4.98 mL of 0.00200 M Fe(NO_3)_3 and 3.97 mL of 0.00200 M KSCN in 1.00 mL water. What is the concentration of FeSCN^+2 if its absorbance at equilibrium was measured to be 0.792? A. 6.75 times 10^4 M B. 6.81 times 10^-2 M C. 2.03 times 10^-4 M D. 1.48 times 10^-4 M
Expert Answer
use formula for absorbance:
A = e*l*c
where:
A is Absorbance
e is molar absorptivity constant
l is length of cell
c is concentration = 0.100 mM = 1.00*10^-4 M
So,
A2/A1 = (c2/c1)
0.792/1.086 = c2 / (2.032*10^-4)
c2 = 1.48*10^-4 M
Answer: D