Determining the Concentration of a Solution: Beer’s Law A= e bc + (0) y = mx + b
ID: 564478 • Letter: D
Question
Determining the Concentration
of a Solution: Beer’s Law
A=ebc + (0)
y = mx + b
A is absorbance on the y axes.
e is the molar absorbtivity with units of L mol-1 cm-1 (M-1cm-1) related to the intensity of the color and constant for a particular aqueous compound/ion at a particular wavelength.
b is the path length of the sample in the cuvette in which the sample is contained. A standard cuvette size is 1cm. The product, eb, is the slope of the line
Calculate the concentration of the Nickel solutions in the first four test tubes in the student data table (below) using the equation MintVint=MfinVfin. M is molarity using units mol/L and V is volume in L or mL as long as the units are consistent.
Fill in the concentration in Molarity using the equation in the table
Trial
number
0.40 M NiSO4
(mL)
Volume Initial Vint
Distilled H2O
(mL)
Concentration (mol/L)
MintVint=MfinVfin
Vfin 10 mL
Mint 0.40 M
Absorbance at Maximum Wavelength
1
2
8
2
4
6
3
6
4
4
8
2
5 (no dilution)
Stock solution directly in Cuvette
0
0.4M
Unknown solution measurement (Do not include in plot)
Trial
number
0.40 M NiSO4
(mL)
Volume Initial Vint
Distilled H2O
(mL)
Concentration (mol/L)
MintVint=MfinVfin
Vfin 10 mL
Mint 0.40 M
Absorbance at Maximum Wavelength
1
2
8
2
4
6
3
6
4
4
8
2
5 (no dilution)
Stock solution directly in Cuvette
0
0.4M
Unknown solution measurement (Do not include in plot)
Explanation / Answer
The question asks to calculate the concentrations of the first four test tubes.
Trial 1:
Mfin = Mint * Vint/ Vfin = 0.4 M * 2 mL/ 10 mL = 0.08 M
Trial 2 :
Mfin = Mint * Vint/ Vfin = 0.4 M * 4 mL/ 10 mL = 0.16 M
Trial 3:
Mfin = Mint * Vint/ Vfin = 0.4 M * 6 mL/ 10 mL = 0.24 M
Trial 4:
Mfin = Mint * Vint/ Vfin = 0.4 M * 8 mL/ 10 mL = 0.032 M
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