1. In this experiment you will be adding Fe(NO3)3 9H20 to KSCN to form a bright

ID: 483272 • Letter: 1

Question

1. In this experiment you will be adding Fe(NO3)3 9H20 to KSCN to form a bright orange complex, [Fe(SCN)] according to the following balanced equation: Fe3 (aq) SCN (aq) [Fe (SCN)P Taqo The resulting equilibrium expression is: [Fe(SCN) leg You are given the following information: [Fe (NO3)3 9H20]stock 0.00350 M [KSCN]stock 0.000700 M Analytical wavelength: 470 nm You make up the solutions to the following specifications: KSCN Vial Fe (NO3)3 9H20 Final volume, mL Number Initial volume, mL Initial Volume, mL (4.00 12.00) 16.00 12.00 4.00 16.00 10.00 6.00 16.00 8.00 8.00 16.00 6.00 10.00 16.00 4.00 12.00

Explanation / Answer

Use the dilution law:

M1*V1 = M2*V2

where M1 = concentration of concentrated solution (initial concentration)

V1 = volume of concentrated solution (stock solution) taken

M2 = concentration of diluted sample

V2 = volume of diluted solution

The total volume (final volume) of the solution is 16.00 mL.

Fill in the table as below:

Vial Number

[Fe3+]I (M)

[SCN-]I (M)

0.000875 (see calculation 1 below)

0.000525 (see calculation 2 below)

0.0013125

0.0004375

0.001750

0.000350

0.0021875

0.0002625

0.002625

0.000175

Calculation 1:

M1 = 0.00350 M, V1 = 4.00 mL, V2 = 16.00 mL.

M2 = M1*V1/V2 = (0.00350 M)*(4.00 mL)/(16.00 mL) = 0.000875 M

Calculation 2:

M1 = 0.000700 M, V1 = 12.00 mL, V2 = 16.00 mL.

M2 = M1*V1/V2 = (0.000700 M)*(12.00 mL)/(16.00 mL) = 0.000525 M