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WorksheetsUV-Visible Spectroscopy
Total questions: 23
Worksheet time: 12mins
Which region does the UV-Visible spectroscopy generally cover?
10-200 nm
200-800 nm
800-2500 nm
0.1-10 nm
The molar absorptivity (ε) has units of
mol/L
L mol-1 cm-1
cm2/g
L/mol
Which of the following compounds is likely to absorb in the UV region?
Alkenes
Alkanes
Saturated hydrocarbon
Alcohols
What is the main principle of UV-Visible spectroscopy?
Absorption of X-rays
Emission of UV light
Absorption of UV or visible light causes electronic excitation
Scattering of UV light
What does λmax represent?
Maximum concentration
Maximum path length
Molar absorptivity
Wavelength of maximum absorbance
The Beer-Lambert law relates absorbance to
Concentration and path length
Wavelength and temperature
Solvent and concentration
Light source and cuvette type
Which of the following factors does not affect UV absorbance?
Solvent polarity
Glass cuvette color
Path length
Temperature
Which chromophore is not active in UV-Visible spectroscopy?
C=C
C=O
-OH
NO2
What is chromophore?
A part of molecule that increase solubility
A group responsible for odor
A catalyst
A group responsible for color/UV absorption
What is an auxochrome?
A group that absorbs UV-Visible light and causes color
A group that deepens the color when attached to a chromophore
A group responsible for emitting fluorescence
A group that causes loss of color in a compound
In UV analysis, a solvent must
Absorb UV light strongly
Be acidic
Be UV transparent in the region of interest
Be basic
What is the typical path length of a cuvette used in UV-Visible spectrophotometers?
1.0 cm
0.1 cm
0.5 cm
10.0 cm
Which detector is commonly used in UV-Vis spectroscopy?
Flame ionization detector
Thermal conductivity detector
Electron capture detector
Photomultiplier tube
Which of the following is true regarding UV-Visible spectroscopy?
It measures emission of radiation
It detects compounds with conjugated system
It is useful for identifying all inorganic compounds
It is only qualitative
Which of the following statements about Beer-Lambert Law is true?
Absorbance is inversely proportional to concentration
Absorbance is independent of path length
The law is valid only for dilute solutions
Absorbance increases linearly with wavelength
What is the typical solvent used in UV-Visible spectroscopy?
Water
Acetone
Chloroform
Ethanol
Why should quartz cuvettes be used for UV range analysis?
Quartz is cheaper
Quartz is chemically inert and resistant to a wide range of common solvents and chemicals
Quartz increases absorbance
Quartz allows more transmission
What will happen to absorbance if the path length of the cuvette is doubled?
Absorption is halved
Absorbance remains the same
Absorbance doubles
Absorbance increases four times
The intensity of absorption is influenced by
The size of the molecule
The number of chromophore present
The temperature of the solution
The pH of the instrument
A solution has ε = 200 L mol-1 cm-1, concentration = 0.01 mol/L, and path length = 1 cm. What is the absorbance?
2.00
0.02
0.20
20.0
If a solution has an absorbance of 0.600, and the molar absorptivity is 150 L mol-1 cm-1, what is the concentration in mol/L (path length = 1 cm)?
0.004 M
0.06 M
0.40 M
0.004 mol/L
A UV measurement of a drug solution gave a %T of 1.00%. What is the absorbance (A)?
2.00
1.00
0.01
3.00
What is the concentration of a solution that shows an absorbance of 1.500 using ε = 300 L mol-1 cm-1 and a path length of 2 cm?
0.0025 mol/L
0.025 mol/L
0.5 mol/L
0.002 mol/L
