# Lab 5 - Calibration Methods and Introduction to UVVIS (1) -...

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Calibration Methods and Introduction to UV-Visible Spectroscopy Type your responses to all questions and embed excel data tables and graphs into one single word document. Before coming to lab: Review Section 4.8 and Chapter 5, Calibration Methods. Read the lab handout. The more time you spend figuring out your dilutions and “recipes” the less time you will have to spend in the lab. Learning Outcomes: Students will apply external standard and standard addition calibration methods to solve the concentration of an unknown (assessed in questions 5,6). Students will understand the differences and uses of external standards, internal standards, and standard addition (assessed in question 8). Students will demonstrate mastery of Microsoft excel for analysis of laboratory data (assessed in questions 1-4,7). SDS: methanol, acetylsalicylic acid Materials 1000 mL volumetric flask 2 – 10 mL volumetric flasks per group. p-1000 micropipettes and tips Concentrated HCl Mortar and pestle Methanol 250 mL storage bottles for the 2% HCl Acetylsalicylic Acid (pure powder) Aspirin Tablets (unknowns) UV-Vis spectrometer set to 236 nm Test tubes and test tube racks Prelab Questions 1. a. (5) Determine the mass of the solute and volume of conc. HCl you are going to weigh out or measure with a graduated cylinder to create one 1L of 100.0 ppm stock solution of Acetylsalicylic acid (ASA) (from the pure powder) in a 2%(v/v) HCl. Show your calculation. b. (5) Describe exactly how you will make the 1 L of 100.0 ppm ASA. When this is weighed out, you must get the mass you have found exactly! 2. (5) Create dilution tables to create your standards for the external calibration method given a 100.0 ppm solution and a 10.00 mL volumetric flask and a micropipet with a range from 100.0 to 1000. µL. Use C 1 V 1 =C 2 V 2 . 3. (5) Create a procedure and dilution for a 325 mg/tablet ASA to be placed in a 1L volumetric flask and diluted to 10.00 ppm in a 10.00 mL volumetric using a micropipette.