lab 3

Riboflavin, also known as vitamin B2, has a molar absorptivity coefficient of 3 x 10 ^3 . If the absorbance reading at a Lmax = 350 nm is 0.90 using a 1 cm cell, what is the concentration of riboflavin in the sample. a. 3.0 x 10^-4 b. 8.57 c. 1.80 x 10^3 d. 9.45 x 10-5

Many ions form colored solutions when dissolved in water. For example, aqueous Cu2+ solutions are light blue and aqueous Ni2+ solutions look light green. These metals in particularare often found in stainless steel. Would you expect their presence in your samples to interfere in the spectrophotometric analysis of permanganate at 525 nm? Why or why not?   I think the answer is that I would expect the Cu2+ in my samples to interfere but not Ni2+ because the Ni2+ is green, signifying a higher wave length that the spectrometer wouldn't be able to pick up on because it was only set to 525 (blue-ish) where as the green is 530-ish. I just want to make sure thanks!

Beaker Volume of KSCN No solution 1 0.50 mL 9.50 mL Part I: Data for Calibration Graph Accurate Concentration of potassium thiocyanate, KSCN stock solution: 0.001 M 0.2 M Fe(NO3)3- Iron(III)nitrate solution: 0.5M Volume of HNO3 solution 0.2 M Volume of 0.2 M Fe(NO3)3 solution 10.00 mL Absorbance 0.037 2 1.00 mL 9.00 mL 10.00 mL 3 2.00 mL 8.00 mL 10.00 mL 4 3.00 mL 7.00 mL 10.00 mL 0.122 0.313 0.547 5 4.00 mL 6.00 mL 10.00 mL 6 5.00 mL 5.00 mL 10.00 mL 0.791 0.868

For the prelab today, all solutions were made using the procedure as outlined in your lab manual. When the absorbances of the solutions were measured, the following data were collected: Part 1 Part 2 Solution Absorbance Solution Absorbance 1 0.000 1 0.000 2 0.300 2 0.343 0.450 0.498 4 0.600 0.642 0.750 5 0.777 Use the data given above to calculate the average value of K for the equilibrium: Fe* (aq) + SCN' (aq) - Fe(SCN)2*(aq) Average K = 3. 4- 3.

For my lab I had to find the unknown concentration of a solution. I found wavelength max of the potassium chromate. Then used that max to find the absorbtion for my sample dilutions. Based on my attached graph. Is my unknown concentration #  making sense? Or did I make an error with the absorbance I wrote down in the lab. I did my calculations when I got home. They are correct, but my unknown concentration amount doesn't look like it will even be on the graph. Or am I wrong. Please  advise and explain. Thank you

22. Can you explain Beer's Law and how to solve problems which involve it?

The best fit curve line to an absorbance vs. concentration plot for standard solutions of a dye has a slope of 0.1815 mL/mg and intercept of 0.0477. A sample solution prepared of the same dye has an absorbance of 0.464 at the wavelength used to establish the Beer's law plot. What is the concentration of dye in the prepared solution? Select one: O a. 0.132 mg/mL b. 2.29 mg/mL O c. 0.464 mg/mL O d. 2.82 mg/mL e. 0.0365 mg/mL Next page Law Tutorial Part 2 Jump to... Exp #9 - Laboratory Practical► Worksheet étv A

Suppose a future student receives an copper sulfate solution unknown that is so darkly blue that no light can be transmitted through the sample and she can't determine the concentration. What should she do? A) Discard the copper sulfate solution in the chemical waste container. B) Dilute the copper sulfate solution with a carefully measured volume of water and try the measurement again. C) Add a few millilters of water directly to the cuvette to get a solution with lighter color. D) Ask her lab partner what their results were and just use the partner's data.

The following absorbance values for four solutions with known MnO4 concentrations were measured using a spectrophotometer: Solution 1 2 3 4 [MnO4] 0.700 x 104 M 1.00 x 104 M 2.00 x 104 M 3.50 x 104 M Absorbance 0.175 0.250 0.500 0.875 A. Using Microsoft Excel, plot a graph of Absorbance vs. Concentration of MnO4. Write the trendline linear equation from the plotted graph. B. Determine the slope of the graph and include its units. C. Determine the concentration of an unknown MnO4 sample whose absorbance is 0.780.

The protein content of the unknown samples were determined using BSA as standard. The absorbance values of the standard solutions and samples are as follows. BSA concentration (mg/mL) Absorbance 0.000 20 0.110 40 0.192 60 0.248 80 0.325 100 0.400 120 0.460 a. What is the equation of the line? b. Determine the protein concentration of samples in ug/mL. Sample dilutions 1 in 14 A540 0.150 1 in 5 1 in 8 0.380 0.235

A copper (II) sulfate solution of unknown concentration is placed in a colorimeter and an absorbance reading of 0.46 is recorded. Using the same solution cell, a 0.055 M of copper (II) sulfate gives an absorbance reading of 0.34. What is the concentration of the first solution?   A. 0.041 mol dm-3   B. 8.60 x10-3 mol dm-3   C. 0.35 mol dm-3   D. 0.074 mol mol dm-3

Cathode Ray Discharge Tube Demonstration An Exploration (Because of the DANGER involved and the fragile nature of the device, this is a demonstration rather than a true Exploration) Background information: Until recently, almost all televisions used a device known as the cathode ray tube, or CRT, to display the images. In a cathode ray tube, the "cathode" is a heated filament (not unlike the filament in a normal light bulb). The heated filament is in a vacuum created inside a glass envelope or "tube." The "ray" is a stream of electrons that naturally pour off the heated cathode into the vacuum. The Cathode Ray Tube is powered by an extremely high voltage DC current system and is dangerous! Electrons are negative. The anode is positive, so the anode attracts the electrons pouring off the cathode. The electrons hit the phosphorus screen and generate green photons, which we can see. Safety: The cathode ray discharge tube is not a toy and should be handled with a lot of precaution. An…

please answer #10

1. What factors are included in the Beer's law expression for determining how much light passes through a liquid solution? 2. How would your test results be affected if you left fingerprints on the sides of the cuvette in line with the light path of the spectrometer (or colorimeter)? 3. The chemical sunset yellow, also known as yellow #6, looks yellow. What color(s) must be absorbed by this chemical? RED YELLOW GREEN WHITE CYAN MAGENTA RGB System (Transmitted light) Additive color system colored light Rendered with Corel Draw 9 RGB pollete 40 M iscalled BLUE-VIOLET 4. Sunset yellow has an extinction coefficient of 20,000 M-1 cm-1 at a lambda max of 470 nm. What is the concentration of a solution that has an absorbance of 0.893?

1. Write the balanced chemical equation for the reaction of Na2S2O3 and HCl in aqueous solution. 2. Consider the following experiment. Twenty mL of a 1.00 M HCl solution is added to 100 mL of a 0.100 M aqueous solution of sodium thiosulfate. After 40 seconds, the reaction has produced enough sulfur to cause a decrease in the percent transmittance to 90%T. If this reaction is repeated using 0.05 M sodium thiosulfate, how long should it take for the reaction mixture to give a 90%T reading if the reaction is first order with respect to Na2S2O3? Second order? Third order? Explain.

© Macmillan Learning The spectroscopic data in the table is generated with five solutions of known concentration. Concentration (M) 0.0163 m = 0.0326 0.0652 0.130 0.261 Absorbance 0.1233 0.2143 0.5231 0.8887 2.008 Use a spreadsheet program, such as Microsoft Excel, to graph the data points and determine the equation of the best-fit line. What is the slope of the linear regression line formed by these points? M-1

In today’s experiment, you will be using the following relationship: A = εcl What does the symbol l represent in this equation?  - concentration - molar absorptivity - path length of the solution - charge - absorbance

You have prepared several dilutions of a standard compound. You measure the absorbance of each solution at 340 nm using a 1 cm cuvette and your results are listed in the table below. Determine the concentration of an unknown sample with an absorbance of 0.085 at 340 nm. Concentration (uM) Absorbance at 340 nm 2. 0.009 4. 0.020 0.061 16 0.111 32 0.189