Question

1) What is the concentration of Fe3+ (after mixing but before reacting) in a solution made with 2.73 mL of 0.0639 M Fe(NO3)3 and 3.89 mL of 0.0231 M KSCN? Please include units in your answer.

2) What is the concentration of a CV solution measured in a 1 cm cuvette with an absorbance of 0.559 and a molar absorptivity of 4560 M^-1cm^-1? Please include units in your answer. Report your answer in decimal format to three significant figures.

Answer 1

Solution :-

1) What is the concentration of Fe3+ (after mixing but before reacting) in a solution made with 2.73 mL of 0.0639 M Fe(NO3)3 and 3.89 mL of 0.0231 M KSCN? Please include units in your answer.

Solution :- M 1 = 0.0639 M , V1 = 2.73 ml

M2 = ?

V2 = 2.73 ml + 3.89 ml = 6.62 ml

Concentration of the Fe3+ after mixing M2 = M1*V1/V2

                                                                  = 0.0639 M * 2.73 ml / 6.62 ml

                                                                  = 0.0264 M

2) What is the concentration of a CV solution measured in a 1 cm cuvette with an absorbance of 0.559 and a molar absorptivity of 4560 M^-1cm^-1? Please include units in your answer. Report your answer in decimal format to three significant figures.

Solution :- molar absorptivity = 4560 M-1 cm-1

Formula

A= e * b *c

e= molar absorptibity

b= pathlength

c= concentration

A= absorbance

0.559 = 4560 M-1 cm-1 * 1 cm * c

0.559 / 4560 M-1 cm-1 * 1 cm= c

1.23*10^-4 M = c

So the concentration is 1.23*10^-4 M