1.0 INTRODUCTION Chemistry is an experimental science. It depend upon carefully observation and the use of good laboratory techniques. Most of experiment in the chemistry laboratory involve quantitative analytical producer. It is involve the common glassware foe example buret, pipette, volumetric flask etc. These glassware are used to measure the volume of the solutions at certain temperature. The volume of the liquid change with the temperature, to get the accuracy, the apparatus involve to measure the volume of solutions have to be calibrated before used. Mistakes and errors can happen during an experiment. Error on the other hand, account for the range of values obtained from successive measurements of the same quantity. Error may be either systematic or random. A systematic error will influence the accuracy of a measurement. A random error will be the evident when a measuring device, even a very accurate one, is used a number times to make the same measurement. Both error can be reduce by using calibrated apparatus and careful when doing experiment.
2.0 OBJECTIVE To learn the qualitative and quantitative aspects of common laboratory equipment and to expose student to the factors that affect the accuracy of an experiment.
3.0 APPARATUS 3.1 Volumetric flask Analytical balance, volumetric flask 25 mL, thermometer
3.2 Pipette Analytical balance, pipette 25 mL, beaker 50 mL, thermometer
3.3 Buret Analytical balance, Buret, beaker 50 mL
4.0 Chemicals Distilled water
5.0 PROCEDURES 4.1 Calibration of volumetric flask 1. Clean and dry a 25 mL volumetric flask and weigh accurately using analytical balance. Record the weigh. 2. Fill the volumetric flask with distilled water and weigh again. Record the weigh. 3. Record the temperature of distilled water. 4. From table 1, determine the actual volume of the volumetric flask
4.2 Calibration of Pipette 1. Clean and dry a 50 mL beaker and weigh accurately using analytical balance. Record and weigh. 2. Clean a pipette (20 mL or 25 mL) and rinse with distilled water. 3. Fill the pipette with distilled water using the procedures that have been discuss in the introduction part. 4. Drain the distilled water into the beaker and weigh again. Record the weigh. 5. Repeate step 1-4 one more time and record the temperature of the distilled water. 6. From the table 1, determine the actual volume of the pipette.
4.3 Calibration of Buret 1. Clean and dry a 50 mL and weigh accurately using analytical balance. Record the weigh. 2. Clean and rinse a buret using distilled water and the gill in the buret with water until the zero mark. 3. Drain 5 mL of the water from the buret into the beaker and weigh as soon as possible. Record the weight. 4. Repeat step 3 by draining water from the buret until the following buret reading become 10 mL, 15 mL, and 20 mL. Record the weigh every time after adding 5 mL water. 5. From table 1, determine the actual volume for every addition of 5 mL of distilled water.
7.0 DISCUSSION Most of the experiment in the chemistry laboratory involve quantitative and analytical producer. The common glassware used to measure the volume of the solution at certain temperature. The volume of a liquid change with the temperature to get accuracy. The apparatus involve to measure the volume of the solution have to be calibrated before used to avoid or reduce systematic and random error during experiment. The volumetric flasks are used to make solutions of known concentration by the dissolution of a known mass of solid or the dilution of a more concentrated solution. Some frequently used volumes in General Chemistry lab are 10.00, 25.00, 50.00, 100.00, and 250.00-mL flasks. At times the zeroes to the right of the decimal point are omitted. However, these zeroes must always be considered in calculations, as they indicate the accuracy of the volume measurement. Pipettes are glass vessels that are constructed and calibrated so as to deliver as precisely known volume of liquid at a given temperature. Transfer pipettes come in many size, but 5 mL, 10 mL, 20 mL, 25 mL pipette are usually found in general chemistry laboratories. The actual volume of solution can be measured by weighing the solution that has been transferred using that pipette. From the density of the solution, we can calculate the volume of the solution. A burette is a vertical cylindrical piece of laboratory glassware with a volumetric graduation on its full length and a precision tap, or stopcock, on the bottom. It is used to dispense known amounts of liquid reagent in experiments for which such precision in necessary, such as a titration experiment. To calibrate the buret, transfer several volumes of solution from the buret and weigh accurately. From the density of the solution, we can calculate the volume of the solution that have been transferred.
8.0 CONCLUSION As the conclusion, all experiment must be done on time and perfectly to get the best result. Avoid random and systematic error during the experiment. Volumetric flask, buret, and pipette are usually used in laboratory. All student must know how to used it correctly.
9.0 QUESTIONS 1. How do you overcome or reduce the problem of random and systematic error while doing an experiment? By used calibrated apparatus, take the reading several times and carefully when doing the experiment also follow the procedure that has been showed before doing the experiment. 2. In what situation do use a volumetric flask, conical flask, pipette, and graduated cylinder? Explain your answer from accuracy aspects of these apparatus.
3. Explain how to read a burette. What are the factors to be considered while using the buret. The typical 50 mL buret has markings every tenth of a mL, but you can estimate whether the meniscus is closer to a mark or half-way between two marks, so that allows us to measure to a limit of 0.05 mL. Therefore, while you can write the volume to two decimal places, the rightmost decimal place can only be a zero or a five. You can't estimate any more precisely than that.
10.0 REFERENCE www.instruction.greenriver.my www.faculty.ccbcmd.edu.my Laboratory manual for Principles of General Chemistry J.A. Beran/ 8th ed/ 2009/ Jeunine Furino/ GGs Book Science
