standared (1) 0.00200 MNaSCN 0.00ml,0.200 Fe(No3)3 25.0ml,0.250 MHNO3 dilute to

ID: 484504 • Letter: S

Question

standared (1) 0.00200 MNaSCN 0.00ml,0.200 Fe(No3)3 25.0ml,0.250 MHNO3 dilute to 100.00ml

standard( 2 ) 0.00200 M NaSCN 2.00ml,0.200 Fe(No3)3 25.00ml,0.250 M HNO3 dilute to 100.00m.

standard (3) 0.00200 M NaSCN 5.00ml,0.200 Fe(No3)3 25.00ml,0.250 M HNO3 dilute to 100.00m.

standard (4 ) 0.00200 M NaSCN 10.00ml,0.200 Fe(No3)3 25.00ml,0.250 M HNO3 dilute to 100.00m.

standard 5 ) 0.00200 M NaSCN 15.00ml,0.200 Fe(No3)3 25.00ml,0.250 M HNO3 dilute to 100.00m.

Show all necessary calculations to complete this table for standard solution 2, marked with a. Use the appropriate data to plot your calibration curve using Excel or similar program and attach that plot after this page in your report. Be wire to reread step B3 of the procedure before graphing.

Explanation / Answer

1. Make the table as given and find out the molar concentrations:

Solution

[NaSCN] added (M)

0.00200

mL NaSCN solution added

Moles NaSCN added

4.0*10-6 (sample calculation 1 below)

1.0*10-5

2.0*10-5

3.0*10-5

Total volume of solution

100

[SCN-]initial (M)

0.0

4.0*10-5 (sample calculation 2 below)

1.0*10-4

2.0*10-4

3.0*10-4

[Fe(SCN)2+]equilibrium

Some data like the value of the equilibrium constant or the extent of the reaction is required; else the concentration of [Fe(SCN)2+]equilibrium must be known to proceed further.

100 (sample calculation 3 below)

92.90

74.47

41.97

22.85

Absorbance

0.000

0.032

0.128

0.377

0.641

Calculation 1:

Moles of NaSCN = (volume of solution in L)*(concentration of NaSCN in mol/L) = (2 mL)*(1 L/1000 mL)*(0.00200 mol/L) = 4.0*10-6 mole.

Calculation 2:

Initial molarity of SCN-, i.e, [SCN-]initial = (moles of NaSCN)/(total volume of solution in L) = (4.0*10-6 mole)/[(100 mL)*(1 L/1000 mL)] = 4.0*10-5 mol/L = 4.0*10-5 M

Calculation 3:

Absorbance (A) and percent transmittance (%T) are related by the equation

A = 2 – log (%T)

When A = 0,

0 = 2 – log (%T)

===> log (%T) = 2

===> %T = 102 = 100

2. We need to know [Fe(SCN)2+]equilibrium to plot the data. Please provide.