Record measured absorbance for each tube in following table. Complete the table by calculating the [ Fe(SCN2+)]eq and [Fe3+]initial and [HSCN]initial
Data:
Volume of 2.00 x 10-3 M Fe(NO3)3 solution, mL 1)5.00, 2) 5.00, 3) 5.00 4) 5.00 5) 5.00
Volume of 2.00 x 10-3 M HSCN solution, mL 1)1.00 2) 2.00 3) 3.00 4) 4.00 5) 5.00
Volume of 0.500 M HNO3 solution, mL 1) 4.00 2) 3.00 3) 2.00 4) 1.00 5) 0.00
Abs. 1) 0.113 2) 0.218 3) 0.324 4) 0.459 5) 0.550
To calculate the [Fe(SCN2+)]eq, [Fe3+]initial, and [HSCN]initial values, we need to use the measured absorbance values and the known concentrations of the Fe(NO3)3 and HSCN solutions.
First, let's calculate the initial concentrations of Fe3+ and HSCN in each tube:
1) For Tube 1:
- Concentration of Fe(NO3)3 = 2.00 x 10-3 M (given)
- Volume of Fe(NO3)3 solution = 5.00 mL (given)
- Initial moles of Fe(NO3)3 = Concentration x Volume = (2.00 x 10-3) x (5.00 x 10-3) = 1.00 x 10-5 mol
- Volume of HSCN solution = 1.00 mL (given)
- Concentration of HSCN = 2.00 x 10-3 M (given)
- Initial moles of HSCN = Concentration x Volume = (2.00 x 10-3) x (1.00 x 10-3) = 2.00 x 10-6 mol
Repeat the same calculations for Tubes 2, 3, 4, and 5 using the given data.
Next, let's calculate the equilibrium concentration of Fe(SCN2+) in each tube using the Beer-Lambert Law. The Beer-Lambert Law states that absorbance is proportional to concentration.
For each tube, we can use the following equation to calculate the equilibrium concentration of Fe(SCN2+):
A = εbc
Where:
- A is the measured absorbance
- ε is the molar absorptivity (a constant value)
- b is the path length of the cuvette (assumed to be 1 cm)
- c is the equilibrium concentration of Fe(SCN2+)
We can rearrange the equation to solve for c:
c = A / (εb)
Given that ε and b are constant for all tubes, we can use the measured absorbances to calculate the equilibrium concentrations of Fe(SCN2+) for each tube.
Finally, let's calculate the [Fe(SCN2+)]eq, [Fe3+]initial, and [HSCN]initial values using the information we have:
[TUBE #] | [Measured Absorbance] | [Fe(SCN2+)]eq | [Fe3+]initial | [HSCN]initial
------------------------------------------------------------------------------
1 | 0.113 | | |
2 | 0.218 | | |
3 | 0.324 | | |
4 | 0.459 | | |
5 | 0.550 | | |
Using the equation c = A / (εb), we can calculate the equilibrium concentrations of Fe(SCN2+) for each tube. The molar absorptivity (ε) constant depends on the specific compound being measured and can be found in literature.
Once we have the equilibrium concentrations of Fe(SCN2+), we can use the balanced chemical equation of the reaction between Fe3+ and HSCN to determine the stoichiometry and calculate the initial concentrations of Fe3+ and HSCN.
Do you have specific values for the molar absorptivity (ε) and the balanced chemical equation?