NAME MARK 1. What passes through your sample to give you an absorbance reading? a. Water C. Blank solution b. Biuret d. Light 2. Which of the following is the correct equation for BeerLambert law? E=A/LC b. A=ELC c C=E/AL L=ACE 3. What does a monochromator do in a spectrophotometer? a. It emits light. b. It is the first type of material measured using a spectrophotometer. C. It breaks up the wavelengths in the light into individual wavelengths d. It breaks a material down into individual atoms. 4. What does a spectrophotometer directly measure? a. The amount of a in a material b. The amount of light that a substance absorbs C. What wavelength of light we are seeing d. The weight of a material 5. A spectrophotometer can be used to (check all that apply): a. determine the presence of a substance in a solution. b. measure the concentration of an unknown solution. C. determine the molecular composition of an unknown substance. d. identify an unknown substance 6. The amount of light absorbed by a sample is called its: a. Absorbance C. Hue b. Transmittance d. Saturation 7. Colorimeter measures the optical density for- a. Colored sample C. Both colored Colorless sample b. Colorless samples d. None of these Problem Asample in a 1.0-cm cell transmits 80% light at a certain wavelength . If the absorptivity of this substance at this wavelength is 2.0.what is its concentration? Solution Problem There is a substance in a solution (4g/liter) The length of cuvette is 2 cm and only 50% of the certain light beam is transmitted. What is the absorption coefficient? Solution

1. What passes through your sample to give you an absorbance reading?<br />Answer: d. Light<br /><br />2. Which of the following is the correct equation for Beer-Lambert law?<br />Answer: b. $A=ELC$<br /><br />3. What does a monochromator do in a spectrophotometer?<br />Answer: c. It breaks up the wavelengths in the light into individual wavelengths.<br /><br />4. What does a spectrophotometer directly measure?<br />Answer: b. The amount of light that a substance absorbs.<br /><br />5. A spectrophotometer can be used to (check all that apply):<br />Answer: a. determine the presence of a substance in a solution.<br />b. measure the concentration of an unknown solution.<br />d. identify an unknown substance.<br /><br />6. The amount of light absorbed by a sample is called its:<br />Answer: a. Absorbance<br /><br />7. Colorimeter measures the optical density for-<br />Answer: a. Colored sample<br /><br />Problem: A sample in a 1.0-cm cell transmits 80% light at a certain wavelength. If the absorptivity of this substance at this wavelength is 2.0, what is its concentration?<br />Solution: To solve this problem, we can use the Beer-Lambert law equation: $A = \epsilon \cdot c \cdot l$, where $A$ is the absorbance, $\epsilon$ is the absorptivity, $c$ is the concentration, and $l$ is the path length. Given that the absorbance is 0.2 (since 80% transmission means 20% absorption), the absorptivity is 2.0, and the path length is 1.0 cm, we can rearrange the equation to solve for the concentration: $c = \frac{A}{\epsilon \cdot l}$. Substituting the given values, we get $c = \frac{0.2}{2.0 \cdot 1.0} = 0.1$ M.<br /><br />Problem: There is a substance in a solution (4 g/liter). The length of the cuvette is 2 cm, and only 50% of the certain light beam is transmitted. What is the absorption coefficient?<br />Solution: To solve this problem, we can use the Beer-Lambert law equation: $A = \epsilon \cdot c \cdot l$, where $A$ is the absorbance, $\epsilon$ is the absorptivity, $c$ is the concentration, and $l$ is the path length. Given that the absorbance is 0.5 (since 50% transmission means 50% absorption), the concentration is 4 g/L, and the path length is 2 cm, we can rearrange the equation to solve for the absorptivity: $\epsilon = \frac{A}{c \cdot l}$. Substituting the given values, we get $\epsilon = \frac{0.5}{4 \cdot 2} = 0.0625$ L·g$^{-1}$·cm$^{-1}$.