[FeSCN] 2+ You mixed Fe(NO 3 ) 3 and KSCN together in part A.These two reactants

ID: 228497 • Letter: #

Question

[FeSCN]2+

You mixed Fe(NO3)3 and KSCN together in part A.These two reactants formed [FeSCN]2+ as a product:Fe3+ + SCN- FeSCN2+

If you assume that Fe3+ is the limiting reagent, and that all of the iron reacted to form the product, then you can assume that the concentration of Fe3+ added to the test tube is the same as the concentration of the product:[Fe(NO3)3] = [FeSCN]2+

Using M1V1 = M2V2, find the concentration of the product, [FeSCN]2+, for each test tube and fill in table A1 above.Use Table 5.2 in your lab manual to find the final volume.

Show an example of how you calculated [FeSCN]2+ for test tube one. Show all units and circle your final answer.

Concentration of iron(lI) nitrate, [Fe(NO:)a]: 2.00x 10-4M Concentration of potassium thiocyanate, [KSCN]: 1.00 M Table A1: FescN* TestVolume of tube 2.00 104 M Absorbance [FesCNI+ step 1 Fe(NOs)3 (mL) 2 3 4 1.00 2.00 3.00 4.00 .012 002 012 021

Explanation / Answer

We shall use the relation

M1*V1 = M2*V2

where M1 = concentration of Fe2+ in the stock solution; V1 = volume of stock solution taken; M2 = concentration of Fe3+ in the stock solution = concentration of [FeSCN]2+ and V2 = final volume of the test solution.

We have V2 = 10.00 mL; plug in values and obtain

(2.00*10-4 M)*(1.00 mL) = M2*(10.00 mL)

====> M2 = (2.00*10-4 M)*(1.00)/(10.00) = 2.00*10-5 M (ans).

Fill in the table.

Test Tube

Volume of 2.00*10-4 M Fe(NO3)3 (mL)

Absorbance

[FeSCN]2+ (M)

1.00

2.00*10-5

2.00

4.00*10-5

3.00

6.00*10-5

4.00

8.00*10-5