chem lab exp. 2

chem lab exp. 2 - Laboratory 2. Density of Liquids and Use...

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Laboratory 2. Density of Liquids and Use of Volumetric Glassware . Name: Norkhairin Yusuf Section Section 40, Monday 2 PM Performed: 15 September, 2008 Submitted 22 September, 2008 Laboratory Instructor: Hongmei Yuan Your Signature ___________________________________
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Purpose The purpose of this lab was to attain skills in working with volumetric pipets and volumetric flasks while measuring mass and volume to determine the density of liquids. Knowing how to calibrate a 10-mL volumetric pipet, 100-mL volumetric flask, prepare a solution, and determine the density of solutions. Introduction A volumetric glassware is designed specifically to accurately contain or deliver a specific amount of a liquid, measured in volume and recorded in units of milliliters (mL) or liters (L). 1- A graduated (or measuring) pipet is a glass column, with lines that indicate various fractions of the total volume. A 5-mL graduated pipet will be marked with 1-mL major division, and further subdivided into 0.1mL parts, and as for 1-mL graduated pipet would be marked with 0.1-mL major divisions and then further subdivided into 0.01-mL subdivisions. 2- A volumetric pipet usually has a bulb in the middle and is not graduated with lines. It is designed to deliver one specified volume. For example a 5-mL volumetric pipet, filled to the line correctly, would have exactly 5.00mL. 3- A volumetric flask is designed to contain a specified amount of liquid-solution. Preparing a solution in the flask. The solute (either liquid or solid) is measured and transferred to the flask and then the solvent (distilled water) is added and then swirl the flask to dissolve the solute. A dropper is used when the amount of solvent added approaches the line on the neck of the flask. This will go on until the bottom of the meniscus is on the line. Experimental PART A: CALIBRATION of the PIPETS [1] A 10-mL volumetric pipet, 10-mL graduated or measuring pipet, and a 100-mL volumetric flask was obtain. All of the apparatus were clean with soapy water, rinsed several times with tap water and later with distilled water. [2] 200 mL of distilled water was obtain in a clean 250-mL beaker. We practiced using the 10-mL graduated and measuring pipets until comfortable with the procedure. [3] The mass of 150-mL beaker is obtained to the nearest milligram (mg). Using the 10-mL volumetric pipet, 10 mL of distilled water is transferred to the beaker and reweighed it. Numbers are recorded. Then, another 10 mL portion of distilled water from the pipet is transferred to the same beaker and reweighed. The same process is done for the third time. The temperature is also recorded using the thermometer.
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[4] Procedure [3] are repeated but using the graduated 10-mL pipet instead of the volumetric pipet. The data is recorded. PART B: CALIBRATION of the 100-mL VOLUMETRIC FLASK
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chem lab exp. 2 - Laboratory 2. Density of Liquids and Use...

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