experiment‚ solutions containing FeCl3 and KSCN‚ diluted in HCl‚ were measured for their absorbance using a UV-Vis spectrophotometer. Upon computing for the molar concentrations of the reagents‚ determining absorbance‚ and noting the length pathway of the instrument (cuvette)‚ the Beer-Lambert’s law was applied to find the molar absorptivity constant‚ denoted ε. Having found ε‚ the equilibrium concentrations of all species were determined‚ and those values were used to find the equilibrium constant
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the determination of Keq of the Fe(SCN)2+ formation (solutions with unknown concentrations). Absorbance readings of the standard and unknown solutions were obtained through the spectrophotometer. The equation of the trend line of the calibration curve (obtained through the plot of the absorbance readings vs. thiocyanatoiron (III) ion concentration of the standard solutions) is given by y = 4041x – 0.049. Using the absorbance readings and the application of the Beer-Lambert Law on the trend line equation
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transmittance or absorbance. Transmittance is the ratio of light passing through the sample (I) to light passing through the control (I0). Absorbance is the negative logarithm of transmittance: The absorbance of a solution depends on three things: the nature of the solution‚ the distance the light travels through the solution (called the path length)‚ and the concentration of the solution. This is summarized by the Beer-Lambert Law‚ A = abc • A is the measured absorbance • a is a constant
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brass by UV-visible spectroscopy. 2. Properly calibrate and use a spectrophotometer. 3. Convert percent transmittance to absorbance‚ and vice versa. 4. Construct a calibration curve relating absorbance and concentration for solutions of known concentrations. 5. Use a calibration curve to determine the concentration of an unknown solution. 6. Convert a molar concentration to a mass percent value. INTRODUCTION Electromagnetic radiation‚ of which ultraviolet and visible light are but two
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spectrophotometric analysis‚ the concentration of a solute is measured in a solution by measuring the amount of light that is absorbed by the solution in a cuvette placed in a spectrophotometer. A spectrophotometer measures the intensity of light after it is directed through and emerges from a solution. In general‚ the higher the concentration of an analyte‚ the higher the absorbance. Spectrophotometric analysis exploits Beer ’s Law‚ which predicts a linear relationship between the absorbance of the solution and
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a reaction introduction Coloured solutions absorb some of the wavelengths in the visible region of the electromagnetic spectrum. A colorimeter can be used to measure the amount of light absorbed by a solution (the absorbance) and this is proportional to the concentration of the coloured species present. In this experiment you will use a colorimeter to investigate the reaction between bromine and methanoic acid:- Br2 (aq) + HCOOH (aq) ↓ 2Br- (aq) + 2H+ (aq) + CO2 (g)
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Based on the data from the riboflavin spectrum scan‚ the maximum absorbance wavelength for this compound is 446 nm. This was the point between 390 nm and 500 nm at which the absorbance value (0.72) was the highest. A blank tube that has the components of the solution being examined except for the compound of interest is then used in combination to provide an even more accurate reading. Then‚ by using Beer’s Law‚ the molar extinction coefficient for riboflavin was able to be calculated: 14‚400 L/(moles*cm)
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make their product competitive by offering a variety of qualities and ingredients in their protein supplements. A brand of protein powder‚ “Tough Guy”‚ claims that if a person were to dilute 1 gram of protein powder in 100ml of water‚ the final concentration should be approximately 0.40 mg/ml (+/- 5%) protein. The objective of this experiment is to determine whether the manufacturer is telling the truth. MATERIALS AND METHODS One gram of Tough Guy protein powder was added to 100 ml of water. 50 µl
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will begin taking readings of %T. Leave the sample tube in the instrument throughout the data collection process. Obtain readings of %T every minute for at least 15 minutes. Record %T values to one decimal place‚ as this allows you to convert to absorbance and retain three significant figures. When the 15th and final reading has been taken‚ remove the sample from the instrument and prepare to re-zero the instrument with a new NaOH blank in another test tube. Then repeat the entire 15-minute data
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Because the amount of light absorbed or emitted is directly proportional to the number of atoms or molecules. Raw Data and Observations: Please see attached. Results: Red #40: absorbance vs. concentration Blue # 1: absorbance vs. concentration % Composition (Grape): % Composition = (mass of Red #40 dye in sample / total mass of sample) (100%) = (4.068 x10^-4 g / 0.1019 g) (100%) = 3.992 x10^-3 (100%) = 0.399%
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