# How To Calculate Molar Absorptivity

The molar extinction coefficient is a measure of how well a chemical species absorbs a wavelength of light.It allows you to make comparisons without taking into account the differences in concentration or solution length during the measurement.It should not be confused with the extinction coefficient, which is used more often in physics.The standard units are liters per mole centimeter.

### Step 1: A is the Beer-Lambert law for absorbance.

The standard equation for absorbance is A + l + c, where A is the amount of light absorbed by the sample, l is its distance from the solution, and c is concentration.The ratio between the intensity of a reference sample and the unknown sample can be used to calculate absorbance.log10(Io/I) is given by the equation A.The intensity is obtained using a tool.The wavelength that is passed through the solution will affect the absorbance.Depending on the makeup of the solution, some wavelengths will be absorbed more than others.You should state which wavelength is being used for your calculation.

### Step 2: Rearrange the Beer-Lambert equation to find a solution.

We can divide the absorbance by the length and concentration to get the molar absorption on one side of the equation.The basic equation can now be used to calculate the molar absorption for a wavelength.The shape of the container used to measure intensity can affect the absorbance between readings.Molar Absorptivity compensates for the variations.

### Step 3: The variables in the equation can be obtained with spectrophotometry.

A spectrophotometer is a piece of equipment that can measure the amount of light that comes out of a substance.The light that passes through can be used to calculate the absorbance of the solution.Prepare a solution of known concentration.The units for concentration are moles/liter.Measure the length of the piece that holds the liquid samples in the spectrophotometer.Units are measured in centimeters.A measurement for absorbance, A, at a given wavelength, can be obtained using a spectrophotometer.Most wavelengths are measured in nanometers, but the unit for wavelength is meters.Absorbance does not have units.

### Step 4: Plug in the variables and solve the equation.

Plug the values you got for A, c, and l into the equation.Multiply l by c and then divide A by the product.You can measure the absorbance of a solution with a concentration of 0.05 mol/L using acuvette.The absorbance at the wavelength was 1.5.What is the relative strength of this solution?30 L mol cm is 1.5/(1 x0.05).

### Step 5: The intensity of transmitted light can be measured.

Put together three to four concentrations of one solution.Measure the absorbance of one concentration of solution at a wavelength.Move to the highest concentration if you want to start.Keeping track of which absorbance goes with which calculation is more important than the order.

### Step 6: The concentration and absorbance can be plotted on a graph.

Plot each point on a line graph using the values obtained from the spectrophotometer.Plot the concentration and absorbance on the X and Y axes for each individual value.Take a line between the points.The points should form a straight line if the measurement is correct.

### Step 7: The slope of the line-of-best-fit is determined by the data points.

You divide the slope of the line by the number of runs.Divide Y/X by subtracting the X- and Y- values from each other.There is an equation for the slope of a line.The lower point on the line is given the subscript 1.The absorbance at a.2 molar concentration is 0.27.Concentrations are X- values while the absorbance values are Y-values.The slope of the line is calculated using the equation for a line (Y2 – Y1).

### Step 8: If you divide the slope of the line by the path length, you can calculate the molar absorption.

The final step is to divide the path length by the data points.The depth of the Cuvette is used in the spectrophotometer.If 1.4 is the slope of the line and the path length is less than 5 cm, the molar absorptivity is more than 2 L mol cm.