Determination of accuracy of volume marking on glassware

I. PURPOSE OF THE EXPERIMENT

To become familiar with the laboratory environment and to acquire skills in accurately reading and recording measurements from apparatus such as the electronic balance, graduated cylinder, pipette, conical flask, volumetric flask, and burette. One should also be able to light and properly adjust a Bunsen burner.

II. INTRODUCTION

In the laboratory, there is a variety of glassware with volume markings on them. The markings on volumetric glassware are placed much more carefully and more accurately than that on non-volumetric glassware. Hence, the volumetric glassware (graduated cylinders, burettes, pipettes, volumetric flasks, etc) give reasonably accurate indications of volume. Common beakers and conical flask have volume markings on them, but are not intended to give very accurate volume measurements. This glassware is usually only accurate to 5% or less. The density of water can be used to determine the accuracy of volume measurements taken using the various apparatus. Water has a definite density at each temperature.

III.  EXPERIMENTAL

1. Chemicals.............Nil

2. Equipment............Reagent bottle, Beaker ,Graduated Cylinder(Measuring Cylinder), Pipette, Volumetric Flask, and Burette

3. Procedure

1. Graduated cylinder(measuring cylinder)

Wash the measuring cylinder with soap solution and rinse it thoroughly with tap water; shake off the excess water and then rinse it again with distilled water contained in a wash bottle. Weigh and record the mass of empty 100-mL beaker. Make sure it is dry on the outside, though it doesn't dry on the inside. Carefully fill the measuring cylinder with 10-mL of distilled water, record the exact volume that has been added. For the last drops of water, use a dropper in order to position the meniscus at a specific volume marking. Pour out all of this water into the 100-mL beaker, reweight the beaker with its contents, and record the mass. Do not empty the water out of the beaker after the weighting.

Fill the graduated cylinder with 10-mL of distilled water again, record the exact volume of water in the measuring cylinder; pour this sample of water into the beaker.

Repeat this procedure for a third time and record the mass again.

2. Pipette

Carefully wash the pipette with tap water and rinse with distilled water. Weight the empty 100-mL beaker, make sure it is dry outside and record the mass. With the aid of the pipette bulb, draw distilled water into the pipette up to the marking. Transfer distilled water from the pipette into the 100-mL beaker, reweigh the beaker with its contents and record the mass. Do not empty the water out of the beaker after the weighing.

Draw distilled water into the pipette again and pour this sample of water into the beaker.

Repeat this procedure for a third time and again record the mass.

3. Volumetric flask

Carefully wash the volumetric flask with tap water and rinse with distilled water. Pour water into the volumetric flask through the funnel up to the marking. Transfer water from volumetric flask into the beaker and record the mass.

Pour water out of the beaker and refill volumetric flask with distilled water up to the marking. Transfer water from volumetric flask into the beaker and record the mass again.

Repeat the procedure for the third time and record the mass.

4. Burette

Wash the burette with tap water carefully and rinse with distilled water. Mount the burette in the burette clamp holder on the ring stand and iron plate. Dispense 10-mL of distilled water from burette into the beaker. Determine the new burette volume, and record it. Weigh the beaker and water, record the mass. Do not dump out the water after weighting.

Dispense another 10-mL of distilled water from the burette into the beaker. Determine and record the new burette volume. Weigh the beaker and water, record the mass again.

Repeat this procedure for the third time  and record the mass.