Question

You prepare a mixture to use to create a colorimetry calibration curve for FeSCN2+ by mixing these things in a 25.00 mL volumetric flask and then diluting to the volume of the flask. 10.00 mL 0.100 M KSCN 5.00 mL 2 M HNO3 4.00 mL 0.00100 M Fe(NO3)3 What is the concentration of FeSCN2+ in this mixture?

Answer 1

The answer to the question is quite simple

In the flask we have

10.00 mL 0.100 M KSCN

5.00 mL 2 M HNO3

4.00 mL 0.00100 M Fe(NO3)3

As we should know KSCN and Fe(NO₃)₃ will react 1:1 to form. FeSCN²⁺

And Fe(NO3)3 is present in very less amount and KSCN in excess

So similar moles to Fe(NO3)3 will produce of FeSCN²⁺

=( 4/1000) ×0.00100M

= 4 ×10^-6 moles

After dilution same will be present in 25 ml flask

So it's concentration in molarity

= number of moles /volume in L

= 4 ×10^-6 /0.025

= 0.00016

So FeSCN2+ concentration will be 0.00016 Molar

I hope this helps if you have any query or want more detailed explanation feel free to ask in the comments section below.