An unknown was prepared with the concentration of 0.000630 M. A Beer's Law plot was prepared using the absorbance values from standard solutions of ASA and a line drawn through all the points passed through the origin with a slope of 1550.2 M–1 . The expected absorbance and %T values for the diluted aspirin solution prepared by the student is _______ and __________, respectively.
I worked this about an two hours ago. Perhaps for another student.
Normally, the concn curves for spectrophotometric work is done by plotting A (absorbance) on the Y axis and c (concn) on the x axis.
Since you have a straight line, the equation for a straight line is
y = mx + b where m is the slope and b is the y intercept. Since the line passes through the origin, b=0 and the equation becomes y = mx
Changing to the way graphs are made, this beomes A = m*c. The slope in the problem (m) is 1550.2; therefore, the equation becomes
A=1550.2*c.
You have c, calculate A(bsorbance). For transmittance, remember that A = log (1/T) or if you want it in %T directly it is A = log (100/%T)
To determine the expected absorbance and %T values for the diluted aspirin solution, we need to use Beer's Law equation, which relates the concentration of a solution to its absorbance.
Beer's Law equation: A = εbc
Where:
A is the absorbance
ε is the molar absorptivity (also known as the molar absorption coefficient) in M–1
b is the path length of the cuvette (in cm)
c is the concentration of the solution (in M)
In this case, we are given that the unknown solution has a concentration of 0.000630 M and the Beer's Law plot has a line passing through the origin with a slope of 1550.2 M–1.
We can use this slope value (1550.2 M–1) to find the molar absorptivity (ε). The molar absorptivity is the proportionality constant between absorbance and concentration:
ε = slope / path length
Since the line passes through the origin (0,0), the path length (b) can be assumed to be 1 cm.
ε = 1550.2 M–1 / 1 cm
Now we can calculate the expected absorbance (A) of the diluted aspirin solution using the Beer's Law equation. We'll assume that the path length remains the same (1 cm) and the concentration of the diluted solution is the same as the unknown (0.000630 M).
A = εbc
A = (1550.2 M–1) * (0.000630 M) * (1 cm)
Finally, we can calculate the percent transmittance (%T) using the formula:
%T = 100 * 10^(-A)
This formula calculates the percent of light transmitted through the solution based on its absorbance (A).
Now you can substitute the calculated values into the appropriate formulas to find the expected absorbance and %T values for the diluted aspirin solution.