SPECTROPHOTOMETRIC ANALYSIS OF STEEL
I have a known molarity of KMnO4 solution. It was diluted by a factor of 20. Its absorbance is now 1.18. The length of the path is 1 cm.What is the molarity of the new solution.
I think you need the molar absorptivity to solve, and I am not sure that the number that I supplied is the correct number. Chemistry research articles will report different numbers for it, and I know that it is not in CRC handbook. That is why Dr. Bob222 hasn't responded.
Use the following equation:
A=ebc
Where
e=molar absorptivity=1.80 x 104 M-1cm-1
b=length of cuvette
c=concentration (Molarity)
A=absorbance
Plug and Chug
A/eb=c
I apologize, this may be why he hasn't responded.
I may be missing something but if you have a "known molarity" of KMnO4, then it's new concn is just M x 1/20 = ?
I goofed on the "English" part of my answer. It's should be its.
To determine the molarity of the new solution, you can use the equation of Beer-Lambert's Law, which relates the concentration of a solute in a solution to its absorbance. Beer-Lambert's Law is expressed as:
A = εcl
where:
A = absorbance
ε = molar absorptivity (constant for a specific substance at a given wavelength)
c = concentration of the solute
l = length of the path the light travels through the solution (in this case, 1 cm)
In your case, the initial molarity of the KMnO4 solution is known, and it was diluted by a factor of 20. Therefore, the concentration of the new solution is 1/20 times the initial concentration.
Let's assume the initial molarity of the KMnO4 solution is M1 (mol/L). The concentration of the new solution, M2, can be calculated as follows:
M2 = M1/20
Now, we can rearrange the Beer-Lambert's Law equation to calculate the molar absorptivity (ε):
ε = A/(cl)
Substituting the given values, we have:
ε = 1.18/(1 × M2)
Now, we can substitute the value of M2 from the previous calculation:
ε = 1.18/(1 × M1/20)
Simplifying further:
ε = 1.18 × (20/M1)
Therefore, the molarity of the new KMnO4 solution is given by M1 times the factor (1.18 × 20/M1), which simplifies to:
Molarity = 1.18 × 20 = 23.6
So, the molarity of the new solution is 23.6 mol/L.