Article in English: The standard equation for absorbance is A = ɛ x l x c, where A is the amount of light absorbed by the sample for a given wavelength, ɛ is the molar absorptivity, l is the distance that the light travels through the solution, and c is the concentration of the absorbing species per unit volume.  Absorbance can also be calculated using the ratio between the intensity of a reference sample and the unknown sample. It is given by the equation A = log10(Io/I).  Intensity is obtained using a spectrophotometer. The absorbance of a solution will change based on the wavelength that is passed through the solution. Some wavelengths will be absorbed more than others depending upon the makeup of the solution. Remember to state which wavelength is being used for your calculation. Using algebra we can divide absorbance by the length and the concentration to get molar absorptivity on one side of the equation: ɛ = A/lc. We can now use this basic equation to calculate molar absorptivity for a given wavelength. Absorbance between readings can vary due to the concentration of the solution and the shape of the container used to measure intensity. Molar absorptivity compensates for these variations. A spectrophotometer is a piece of equipment that passes a specific wavelength of light through a substance and detects the amount of light that comes out. Some of the light will be absorbed by the solution and the remaining light that passes through can be used to calculate the absorbance of that solution.  Prepare a solution of known concentration, c, for analysis. Units for concentration are molar or moles/liter.  To find l, measure the length of the cuvette, the piece that holds the liquid samples in the spectrophotometer. Units for path length are measured in centimeters. Using a spectrophotometer, obtain a measurement for absorbance, A, at a given wavelength. The unit for wavelength is meters, but most wavelengths are so small, they are actually measured in nanometers (nm). Absorbance has no units. Using the values you obtained for...

Summary in Vietnamese:
Tìm hiểu định luật hấp thụ Beer-Lambert, A = ɛlc. Chuyển vế phương trình Beer-Lambert để tính độ hấp thụ mol. Tìm giá trị các biến số trong phương trình bằng phương pháp quang phổ kế. Thay giá trị vào các biến số và giải phương trình tìm độ hấp thụ mol.