Precision en Quimica

Student: Edwin Montiel        

Date: September 9, 2016

Accuracy and Precision Experiment Pre Lab #1

Objective:

Know which glassware should be used in various circumstances. Know how to correctly measure volume and mass. Become familiar with significant figures and its relationship to measurements and data recording (significant figures). Become familiar with the errors, precision and accuracy associated the various measurement tools and techniques. Determine the density of liquids and solids. Determine the best-fit straight line as a method to examine linear relationships and to use this relationship as a predicative model such as in the determination of the percent copper and zinc in pennies based on density measurements. Record laboratory data and observations.

Background:

Some glassware is very carefully designed and marked for high accuracy/precision work such as burets, pipets, and volumetric flasks, while other glassware is not intended for such work. In high accuracy/precision work, the glassware must be clean. Not only does clean glassware avoid unwanted chemical contamination, but it also assures that delivered volumes of liquids will be correct. A dirty spot on the inside wall of a burette or pipet, for example, even if the spot itself does not occupy a significant volume, can cause a droplet of water to adhere to the wall, causing an error in the recorded volume of delivered liquid (less volume delivered)

Procedure:

 In lab, we did an experiment to determine the accuracy and precision for the measurement of volumes for eight devices: Measure the mass of a clean, dry, empty 125-mL Erlenmeyer Flask. Carefully fill this flask to the 100-mL mark (using the marks on the flask) with deionized (distilled) water. Determine the final mass of the flask and water. Use the density formula to determine the exact volume of the water. Repeat this procedure with all the other trials. Calculate the precision and accuracy parameters.

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