Because it's a relative value.
The absorbance value for tartrazine will depend on the specific wavelength at which it is measured. Tartrazine typically absorbs light most strongly in the visible spectrum, around 425-430 nm. To determine the exact absorbance value, you would need to measure the absorbance of a known concentration of tartrazine at this wavelength using a spectrophotometer.
To calculate the concentration of NaCl from an absorbance value, you typically use Beer's Law, which states that absorbance (A) is directly proportional to concentration (C). The equation is A = ε * l * C, where ε is the molar absorptivity and l is the path length of the cuvette. By rearranging the equation to solve for concentration, you can use the absorbance value along with known values for ε and l to find the concentration of NaCl. If you have a calibration curve from previous experiments, you can also use it to directly determine concentration from the absorbance value.
because that chart gives a more accurate value than the absorbance scale on the specthometor
thymol blue 436, 545 and 595 nm
Mol-1cm-1
Absorbance is a dimensionless quantity and has no units. It is calculated using the formula A = log10(I0/I), where A is absorbance, I0 is the intensity of the incident light, and I is the intensity of the transmitted light. Since it is a logarithmic ratio of two intensities, absorbance is expressed simply as a number, typically ranging from 0 to 3 for most applications.
The absorbance value for tartrazine will depend on the specific wavelength at which it is measured. Tartrazine typically absorbs light most strongly in the visible spectrum, around 425-430 nm. To determine the exact absorbance value, you would need to measure the absorbance of a known concentration of tartrazine at this wavelength using a spectrophotometer.
To calculate the concentration of NaCl from an absorbance value, you typically use Beer's Law, which states that absorbance (A) is directly proportional to concentration (C). The equation is A = ε * l * C, where ε is the molar absorptivity and l is the path length of the cuvette. By rearranging the equation to solve for concentration, you can use the absorbance value along with known values for ε and l to find the concentration of NaCl. If you have a calibration curve from previous experiments, you can also use it to directly determine concentration from the absorbance value.
because that chart gives a more accurate value than the absorbance scale on the specthometor
Absorbance rises with concentration because there is more material for a given frequency of light to be absorbed in. Your statement is false.
The molar absorptivity of NADH at 340 nm is approximately 6,220 M^{-1} cm^{-1}. To calculate the theoretical absorbance, you can use the formula: Absorbance = molar absorptivity x path length x concentration. Given a concentration of 0.01 M and a typical path length of 1 cm, the theoretical absorbance at 340 nm for a 0.01 M solution of NADH would be 0.01 x 6220 x 1 = 62.2 absorbance units.
In spectrophotometry, optical density (OD) and absorbance are directly related. As the OD increases, the absorbance also increases. This means that a higher OD value indicates a higher absorbance of light by the sample being measured.
A higher absorbance value in a spectrophotometry experiment indicates that more light is being absorbed by the sample, suggesting a higher concentration of the substance being measured.
The slope of a plot of absorbance vs. concentration represents the molar absorptivity (also known as the molar absorptivity coefficient or extinction coefficient) of the compound being measured. It indicates how strongly the compound absorbs light at a specific wavelength, and a higher slope indicates a higher absorbance for a given concentration.
thymol blue 436, 545 and 595 nm
It's over 9000.
Mol-1cm-1