Using the Absorbance (0.455) of your Unknown SCN- solution and the slope (3163.9) from your Calibration Curve, calculate the concentration of SCN- in the solution created from 5.0 mL 0.200 M Fe(NO3)3, 40.0 mL H2O and 5.0 mL SCN-. How would I calculate?
A = ebc where e is the molar absorptivity = slope of the line.
0.455 = 3163.9*c
Calculate c.
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To calculate the concentration of SCN- in your solution, you can use the Beer-Lambert Law, which states that absorbance (A) is directly proportional to the concentration (C) of the absorbing species.
The equation for the Beer-Lambert Law is A = εbc, where A is the absorbance, ε is the molar absorptivity (slope of the calibration curve - in this case, 3163.9), b is the path length (in centimeters), and c is the concentration of the absorbing species (in moles per liter, or M).
Given:
Absorbance (A) = 0.455
Slope (ε) = 3163.9
First, calculate the path length (b). Assuming you have a standard spectrophotometer cuvette with a path length of 1 cm, b = 1 cm.
Now, rearrange the Beer-Lambert Law equation to solve for concentration (c):
c = A / (εb)
Plugging in the values:
c = 0.455 / (3163.9 * 1)
The concentration of SCN- in the solution created is approximately c = 1.44 x 10^-4 M.
Remember, this calculation assumes that the reaction between Fe3+ and SCN- follows a 1:1 stoichiometry.
To calculate the concentration of SCN- in the solution, you can use Beer-Lambert Law. The equation for this is:
A = εbc
Where:
A is the absorbance of the solution (0.455),
ε is the molar absorptivity or the slope of the calibration curve (3163.9),
b is the path length, which is usually taken as 1 cm for cuvettes,
and c is the concentration of the SCN-.
First, we need to find the concentration of Fe(SCN)2+ using the balanced chemical equation:
Fe3+ + SCN- → Fe(SCN)2+
According to the balanced equation, the stoichiometry is 1:1. This means the concentration of Fe(SCN)2+ is equal to the concentration of SCN-.
We are given that the initial concentration of Fe(NO3)3 is 0.200 M and the volume is 5.0 mL (or 0.005 L). So, we can calculate the moles of Fe(NO3)3:
moles Fe(NO3)3 = initial concentration × volume
= 0.200 M × 0.005 L
= 0.001 mol
Since the stoichiometry is 1:1, the moles of Fe(SCN)2+ and SCN- are also 0.001 mol.
Now, we need to calculate the volume of the final solution.
volume final solution = volume Fe(NO3)3 + volume H2O + volume SCN-
= 0.005 L + 0.040 L + 0.005 L
= 0.05 L
Next, we can calculate the concentration of SCN- using the Beer-Lambert Law:
A = εbc
0.455 = 3163.9 × c × 1 (assuming path length is 1 cm)
c = 0.000144 M
Therefore, the concentration of SCN- in the solution is 0.000144 M.
To calculate the concentration of SCN- in the solution, we can use the Beer-Lambert Law, which relates the absorbance of a solution to the concentration of the absorbing species. The equation is as follows:
A = εlc
Where:
A is the absorbance,
ε is the molar absorptivity (slope of the calibration curve),
l is the path length (usually expressed in cm),
and c is the concentration of the absorbing species.
In this case, we have the absorbance (A = 0.455) and the slope (ε = 3163.9). The path length is typically standardized to 1 cm in visible light spectrophotometry. Now, we need to solve for the concentration (c).
Step 1: Calculate the path length (l):
Since l = 1 cm (standardized value), we don't need to perform any calculations for the path length.
Step 2: Rearrange the Beer-Lambert Law equation to solve for concentration (c):
c = A / (ε * l)
Step 3: Plug in the values and calculate:
c = 0.455 / (3163.9 * 1)
c = 0.455 / 3163.9
c ≈ 1.44 × 10^-4 M
Therefore, the concentration of SCN- in the solution is approximately 1.44 × 10^-4 M.