cheer wine lab

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East Carolina University *

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1010

Subject

Chemistry

Date

Dec 6, 2023

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docx

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9

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Lab 7: Ultraviolet-Visible Spectroscopy Yvonne Mwesige The purpose of this lab is to excise the use of calculations for dilute solutions, to perform serial dilutions, identify the basic components and working principles of spectrophotometry, and to generate and use the standard curve to evaluate data. Pre Lab-Questions: 1. Calculate the concentration of a solution made by starting with 25.0 ml of 2.25 M HCl and adding enough water to make the total volume 87.5 ml.
0.64 M 2. A concentration of 355 ppm NaCl in water means that there are 355 mg of NaCl in every liter of water. Determine how many mg of NaCl are present is a 296 ml sample of this solution. 83.3 2. A 100-ppm stock solution of red dye #40 has already been prepared for you by weighing a known amount of red dye, carefully transferring it to a 1-L volumetric flask, and diluting to the mark. How many milligrams of red dye was used when preparing 1 L of the 100-ppm stock solution? Show a calculation to support your answer. Absorbance (A) = C x L x => Concentration (C) = A/(L x ) Ɛ Ɛ 100ppm/(1Lx40) =4,000/1000 = 4ml
Part 1: Preparation of the standard Solutions: Desired Standard Concentration (ppm Stock Solution Concentration (C 1 ) Stock Solution Volume (V 1 ) Dilute Solution Concentration (C 2 Dilute Solution Volume (V 2 ) 2.00 ppm 100 mL 1 2 50 4.00 ppm 100mL 1 4 25 8.00 ppm 100mL 2 8 25 10.00 ppm 100mL 1 10 10 20.00 ppm 100mL 2 20 10 1. Fill in the table below with the information for your standard Solution mL of the 100-ppm stock (C 1 ) (pipette volume, V 1 ) Total mL diluted solution (flask volume, V 2 ) ppm of the diluted solution (C 2 from the calculation) 1 mL 50 2.00 ppm 1mL 25 4.00 ppm 2mL 25 8.00 ppm 1mL 10 10.00 ppm 2mL 10 20.00 ppm
Red Dye Standards records at wavelength = 501.70 nm SAMPLE Absorbance 2 .104 4 .195 8 .375 10 .473 20 .875 (diluted) Cheer wine .680
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