Please help me with these lab questions, addition possible info needed is attach
ID: 515113 • Letter: P
Question
Please help me with these lab questions, addition possible info needed is attached below. 2. What is the advantage of the standard addition method when quantifying something like the iron in a vitamin tablet? 10. IRON BY STANDARD ADDITION-vrTAMINTABLET & NOWN Introduction sau fraut *yon need stock room Iron is an essential mineral that plays an important role in of both hemoglobin and myoglobin. transport since it a component Many metallic complexes in solution concentration of the metal ion solutions we can measure the by using spectrophotometry and Beer's law In this experiment, the determination of dissolved iron (the analyte) is on the strong and ne, a chelating agent, to form a red colored complex At room temperature Fea" 3 o-phenanthroline Felo-phenanthroline) for this react and mildly acidic conditions, the equilibrium constant high, -2.5 x 10, and the complex is very However, Fe is not bound well by o- phenanthroline, stable all Fe is present as the fully reduced, Fe2" so care must be taken to ensure The standard addition method involves adding known quantities of standard solution of the analyte to the unknown. The increased absorbace lets us deduce how much analyte was in the original unknown. In this experiment you will be provided with a standard iron solution rather than making it yourself to illustrate that commercial standards exist and can be purchased for use in analytical situations. Experimental Procedure student should also The vitamin tablet and Fe standard solution work is done as a pair, each select an individual unknown. Dissolving a known vitamin tablet. Each pair choose a known vitamin tablet and note the product information from the bott and record the weight the tablet. (in the hood). Place a 150 mL beaker. Using a graduated cylinder, add ~25 6 M HCl solution a watch glass on the beaker and bring the insoluble matrix components. for about add minutes, the tablet should be dissolved, except for With twice (into Celite (diatomaceous until a slurry is formed. Fold a shark p a clean 100 mL and place it in a in the place the funnel on top of volumetric the tablet solution into the flask. Use a wash bottle to rinse the 150 mL beaker and filter paper thoroughly to assure quantitative transfer. Dilute to the mark with Nanopure water when the solution is at room temperature. Transfer into a clean 125 ml. plastie bottle, cap and label Tab Acquisition of Stock Solutions. All stock solutions are prepared freshly in 100 mL volume flasks and can be shared by 2-3 individuals. Check out clean 1 mL plastic pipets from the stock room to dispense the sodium citrate hydroquinone and o-phenanthroline 1) Sodium Citrate reagent: 2.5 g sodium citrate qsad 100 ml. agent) 2) 1 g uinone qsad 100 ml (reducing then qsad 100 ml. 0.25 g o-phenanthroline di 0 mL ethanol, in with Nanopure water. Ethanol is an organic co-solvent for the sparingly soluble compoundExplanation / Answer
1. This is done to make a calibration curve from where you can calculate the molar extinction coefficient value of Fe-phenanthrolene complex
2. Standard addition method is used whenever you have a very small sample. Amount of Fe in the tablet is very small . So, it is better to used standard addition technique where you measure the Fe concentration indirectly from the graph.