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Measuring Absorbance quiz #1

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  • How do you calculate the percent transmittance of a sample in UV-Vis spectroscopy if its absorbance is 0.419?
    Percent transmittance (%T) is calculated using the formula %T = 10^(-A) × 100, where A is absorbance. For an absorbance of 0.419, %T = 10^(-0.419) × 100 = 38.1%.
  • If a sample in UV-Vis spectroscopy has a percent transmittance of 39.1%, how do you determine its absorbance?
    Absorbance (A) can be calculated from percent transmittance (%T) using the formula A = -log10(%T/100). For %T = 39.1%, A = -log10(0.391) = 0.407.
  • What does absorbance represent in UV-Vis spectroscopy?
    Absorbance represents the quantity of light that a sample absorbs.
  • How is percent transmittance (%T) defined in UV-Vis spectroscopy?
    Percent transmittance is the amount of light that passes through a sample.
  • What is the mathematical relationship between absorbance (A) and percent transmittance (%T)?
    Percent transmittance is calculated as %T = 10^(-A) × 100.
  • If a sample has an absorbance of 0.419, what is its percent transmittance?
    The percent transmittance is 38.1%.
  • How do you calculate absorbance if you know the percent transmittance?
    Absorbance is calculated using the formula A = -log10(%T/100).
  • What is the absorbance of a sample with a percent transmittance of 39.1%?
    The absorbance is 0.407.
  • How are absorbance and percent transmittance related to each other?
    They are inversely related; as absorbance increases, percent transmittance decreases.
  • What happens to light absorption and transmittance as the concentration of a sample increases?
    As concentration increases, the sample absorbs more light and less light is transmitted through it.
  • What does the absorbance value displayed on a spectrophotometer represent?
    The absorbance value represents the quantity of light that a sample absorbs in UV-Vis spectroscopy.
  • What is a calibration curve in the context of measuring absorbance?
    A calibration curve is a plot of absorbance versus concentration for a series of standard solutions, used to determine the concentration of unknown samples.
  • What is the purpose of a calibration curve in analytical chemistry?
    The purpose of a calibration curve is to establish the relationship between absorbance and concentration, allowing for the determination of unknown sample concentrations based on their absorbance.
  • In what units is absorbance measured in UV-Vis spectroscopy?
    Absorbance is a unitless quantity; it has no units.
  • What are the transmission and absorbance values of a blank sample in spectrophotometry?
    A blank sample ideally has 100% transmittance and an absorbance of 0.
  • What is the unit for absorbance in a spectrophotometer?
    Absorbance is unitless; it does not have any units.
  • What units are absorbance measured in?
    Absorbance is measured without units; it is a dimensionless quantity.
  • How are percent transmittance and absorbance related algebraically in UV-Vis spectroscopy?
    Percent transmittance (T) and absorbance (A) are related by the formula: T = 10^(-A) × 100%.
  • How do you calculate percent transmittance from a given absorbance value?
    Percent transmittance is calculated using the formula: percent transmittance = 10^(-absorbance) × 100%.
  • How can you find percent transmittance from absorbance in spectrophotometry?
    Percent transmittance can be found using the formula: percent transmittance = 10^(-absorbance) × 100%.
  • How do you find transmittance from absorbance in UV-Vis spectroscopy?
    Transmittance (as a decimal) is calculated as T = 10^(-A), where A is absorbance.
  • How do fingerprints on a cuvette affect absorbance measurements in spectrophotometry?
    Fingerprints on a cuvette can increase absorbance readings by blocking or scattering light, leading to inaccurate results.
  • What are the units of absorbance in spectrophotometry?
    Absorbance is a dimensionless quantity and has no units.