Concept explainers
(a)
Interpretation:
The percent transmittance and the absorbance of the absorbing solution for the linear readings given by the photometer should be determined.
Concept introduction:
The percent transmittance of a solution is the ability of the solution to allow the monochromatic light to pass through it. The percent transmittance of a solution is the ratio of the intensity of monochromatic light incident on the solution to the intensity transmitted through the solution.
The expression for the percent transmittance for a sample solution is:
The absorbance of the solution is the ability of the solution to absorb the monochromatic light passing through it. The absorbance of the solution is defined as the ratio of the intensity of light incident on the solution to the intensity of light absorbed by the solution.
The relation between the absorbance and transmittance is related by Beer’s law.
(b)
Interpretation:
The transmittance of the solution if the concentration of the absorber is reduced to half of the original solution should be determined.
Concept introduction:
The percent transmittance of a solution is the ability of the solution to allow the monochromatic light to pass through it. The percent transmittance of a solution is the ratio of the intensity of monochromatic light incident on the solution to the intensity transmitted through the solution.
The relation between the absorbance and transmittance is established by Beer’s law.
(c)
Interpretation:
The transmittance of the solution is to be determined if the path length of the light in the cell is doubled.
Concept introduction:
The percent transmittance of a solution is the ability of the solution to allow the monochromatic light to pass through it. The percent transmittance of a solution is the ratio of the intensity of monochromatic light incident on the solution to the intensity transmitted through the solution.
The relation between the absorbance and transmittance is established by Beer’s law.
The absorbance of the solution is directly proportional to the path length of the cell. So, if the path length is doubled, the absorbance of the solution will also be doubled.
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Chapter 13 Solutions
Principles of Instrumental Analysis
- A 50.0 mg sample was dissolved in acid and then diluted to a total volume of 50.00 mL. If 1.000 mL ofthis solution was then diluted to 50.00 mL with water. If this diluted solution had a transmittance of 0.275 at520 nm, what is the concentration of KMnO4 in ppm in this diluted solution, assuming no interference fromother species at this wavelength?arrow_forwardAssuming the transmittance of an absorbing species with a concentration of 0.10 mM is 60%, what would be the absornamce when the concentration is increased to 1.0 mM?arrow_forwardWhat percent transmittance range and what absorbance range are considered to be the optimum working ranges for spectrochemical measurements?arrow_forward
- state the relationship between absorbance and transmittancearrow_forwardAn aqueous solution of triphosphate derivative of molar mass 502 g per mol was prepared by dissolving 17.2 mg in enough water to make 500 cubic cm of solution and a sample was transferred to a cell of length 1 cm. The absorbance was measured as 1.011. Calculate the molar absorbance coefficient and the transmittance for a solution twice the concentration.arrow_forwardA photometer when placed in a blank in light path provides a reading of 700 mV and 170 mV when it was replaced by an absorbing solution. Calculate: a) % transmittance and absorbance of the absorbing solution. b) Transmittance when the concentration of absorber is one half of the original solution. c) Transmittance when the light path through the original solution is doubled.arrow_forward
- The levels of Vitamin B1 in a sample of milk was determined using the Standard Addition method and technique of fluorescence spectroscopy. 18.0 ml of the milk sample was diluted to 20.0 ml using distilled water and then the fluorescence was measured. The resulting signal was 210 units. A spike was made by taking 18.0 ml of the same milk sample, adding 1.0 ml of a 6.0 ppm Vitamin B1 standard solution, and then diluting to 20.0 ml using distilled water. The signal of the spiked milk was 540 units. Calculate the concentration of Vitamin B1 in the original milk sample (in ppm). Report to 3 decimal places.arrow_forwardThienothiophene and sexithiophene are conjugated molecules used in printed organic electronics. A chlorobenzene solution of equal concentrations of the two molecules was prepared and its absorbance was recorded with a 0.01 cm sample cell to give 0.88 % transmittance (T) at 400 nm. Calculate the concentration of each of the molecules given that the molar absorption coefficient of the thienothiophene is 23,000 L.mol-1cm-1 and the sexithiophene is 34,000 L.mol-1cm-1. Remember that absorbance is additive.arrow_forwardBy what factor will you change the concentration as you monitor the absorbance/transmittance of the solution?arrow_forward
- An analyst needs to evaluate the potential effect of an interferent, I, on the quantitative analysis for an analyte, A. She begins by measuring the signal for a sample in which the interferent is absent and the analyte is present with a concentration of 15 ppm, obtaining an average signal of 23.3 (arbitrary units). When analyzing a sample in which the analyte is absent and the interferent is present with a concentration of 25 ppm, she obtains an average signal of 13.7.arrow_forwardAn analyst needs to evaluate the potential effect of an interferent, I, on the quantitative analysis for an analyte, A. She begins by measuring the signal for a sample in which the interferent is absent and the analyte is present with a concentration of 15 ppm, obtaining an average signal of 23.3 (arbitrary units). When analyzing a sample in which the analyte is absent and the interferent is present with a concentration of 25 ppm, she obtains an average signal of 13.7. What is the sensitivity for the analyte? What is the sensitivity for the interfering? What is the value of the selectivity coefficient? What is the maximum concentration of interferent relative to that of the analyte (i.e. interferent/analyte), if the error in the analysis is to be less than 1%?arrow_forwardExpress the following absorbances in terms of percent transmittances.(a) 0.0356(b) 0.379(c) 0.485arrow_forward
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