A student is studying the composition of brass, an alloy mad…
Questions
A student is studying the cоmpоsitiоn of brаss, аn аlloy made from copper and zinc. He places a piece of brass into excess nitric acid, and the copper reacts to make copper (II) nitrate. To determine the concentration of the copper (II) ions in solution, he uses colorimetric (spectrophotometric) analysis. The student first determines the appropriate wavelength to use to analyze the copper (II) ion. Then he analyzes a series of solutions of copper (II) of known concentration with a spectrophotometer that has a 1.00 cm cuvette to generate the following data. Trial Concentration (M) Absorbance 1 0.10 0.28 2 0.20 0.56 3 0.40 1.12 4 0.50 1.41 unknown Unknown from brass sample 1.66 He determines the appropriate wavelength to analyze iron thiocyanate is 635 mn. What is the frequency of this wave? Use the data in the table to calculate the molar absorptivity constant for the copper (II) ions. What is the concentration of copper (II) ions in the unknown solution? If the solution of copper (II) ions analyzed had a volume of 100.0 mL, how many grams of copper reacted with the nitric acid? Show your work. Note: Your answer(s) must be provided in this text box. If you are unable to show your work adequately using the Rich Text Editor, complete your work on scratch paper. Upload a photo of your work in the "Comments" of this exam immediately after you have completed and submitted the exam. You can access the "Comments" through the grade book. Answers on scratch paper alone will not be scored.
In the pаthwаy thаt prоduces tryptоphan, there are 3 enzyme catalyzed steps invоlved in converting the precursor molecule into the finished amino acid. On the left side, a vertical sequence shows the conversion of molecules through enzymatic steps. At the top is a pink rectangle labeled Precursor. A pink arrow labeled Enzyme 1 points downward to a pink pentagon shape. Another pink arrow labeled Enzyme 2 points downward to two connected pink shapes, a hexagon and a square. A third pink arrow labeled Enzyme 3 points downward to two connected pink shapes, a hexagon and a square, which are labeled Tryptophan at the bottom. On the right side, three blue DNA double helix structures are shown vertically. The top helix is labeled trpC gene with a light blue arrow pointing left toward Enzyme 1. The middle helix is labeled trpB gene with a light blue arrow pointing left toward Enzyme 2. The bottom helix is labeled trpA gene with a light blue arrow pointing left toward Enzyme 3. If tryptophan accumulates in the cell, it signals the first enzyme in the pathway to stop converting the precursor molecule. When more is needed, the enzyme will be activated and the pathway will proceed. This type of metabolic control is called ______.