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Chem 142 - Lab 1 - Chemical Measurements

# Chem 142 - Lab 1 - Chemical Measurements - Name Alice Hsieh...

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Lab Partner: DATA AND CALCULATIONS Part A I. Determination of uncertainty in graduated cylinder volume Room temp 22 0.5 pt Density of water at RT 1 g/mL 0.5 pt Run 1 Run 2 Run 3 Run 4 Run 5 Mass of vial + cap (g) 28.2 28.32 28.13 28.37 28.41 Mass of flask + cap + water (g) 37.85 38.1 38.09 38.11 38.11 Mass of water delivered (g) 9.65 9.79 9.96 9.74 9.7 Volume of water delivered (mL) 9.67 9.81 9.98 9.76 9.73 Average volume of water delivered 9.790 mL Standard deviation of measurements ±0.1191 mL Name: Alice Hsieh Duong Hieu o C Provide sample calculations for determining the volume of water from the mass of water, the average volume delivered, and the standard deviation of your measurements. These may be neatly handwritten. (2 pts each = 6 pts) 1. Density = Mass ; Volume = Mass ; Density of water @ 22˚C = 0.99777g/mL Volume Volume For Run 1: Volume of water = 9.649 / 0.99777 = 9.671mL 2. Average volume of water delivered: (9.671 + 9.809 + 9.983 + 9.761 + 9.726) = 9.790mL 5 3: Standard deviation = root[ [(9.671-9.790)² - (9.809-9.790)² - (9.983-9.790)² - (9.761-9.790)² - (9.726-9.790)²] / (5-1) ] = ± 0.1191mL EXP 1: Physical Measurements and Error Analysis Grading WebAssign prelab: 5 pts This template: 30 pts Lab Notebook Duplicate: 5 pts By signing below, you certify that you have not falsified data and that you have not plagiarized any part of this lab report. Failure to sign this declaration will cost you 5 points. Signature: Purpose and Method Things to think about: What is the goal of this experiment? Explain how it is accomplished. What is the general method (not step by step detailed procedure) that you will be using to achieve this goal? How will you process the data that you record in lab? (What calculations will you use and how do you obtain all of the values to plug into those equations?) (5 points) The main goals of this experiment are for us students to become familiar with using different types of measuring equipment, understand the difference between accuracy and precision, as well as enhance our studying on the concept of density. We have three kinds of volumetric glassware, a graduated cyclinder, a buret and a pipiet, to determine the precision of a volume measurement. For each of the measuring equipment, we have several trials to determine the average volume of water delivered by the specific equipment and its precision by calculating and comparing the standard deviation of the measurements. After determining the most precise measuring equipment, we can then evaluate its accuracy by preparing a solution with a known density. In this part of the lab, we use the most precise volumetric glassware to prepare a solution that is 25% sucrose by weight. We can then determine the density of sucrose solution prepared and

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