Concentrations of Fe(SCN)2+ in calibration Solutions: Recall that the concentrat

Question

Concentrations of Fe(SCN)2+ in calibration Solutions: Recall that the concentration of Fe(SCN)2+ in the calibration solutions is essentially the concentration of the SCN- initially in the solution. So, determine the concentration of SCN- in each of the 10.0 mL calibration solutions.

Here are the results of the previous solutions when put through a sceptrometer:

Calibration Solution 0.2 M Fe(NO3)3 in 0.5M HNO3 0.002 M KSCN in 0.5M HNO3 0.5M HNO3 Blank 5.0 mL 0.0 mL 5.0 mL Solution 1 5.0 mL 0.5 mL 4.5 mL Solution 2 5.0 mL 1.0 mL 4.0 mL Solution 3 5.0 mL 1.5 mL 3.5 mL Solution 4 5.0 mL 2.0 mL 3.0 mL

Explanation / Answer

From the data

[SCN-] = molarity of SCN- stock solution x volume of stock taken/total volume of solution

Solution              [SCN-] (M)

Blank                        0

     1             0.002 x 0.5/10 = 0.0001

     2             0.002 x 1/10 = 0.0002

     3             0.002 x 1.5/10 = 0.00015

     4             0.002 x 2/10 = 0.0004

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