Calibration of Volumetric Glassware Essay

Summary In this experiment, The purpose of this experiment is to investigate the measurement of the actual volume contents of volumetric glassware. In the beginning of the experiment, the volumetric glassware should be clean and dry before used. The volumetric glassware, measuring cylinder and pipette should be handled with care and all the precautions were be taken during the experiment was held. This was to ensure to avoid any errors such as parallax error especially while reading water meniscus. This experiment must be repeated three times or more and take the average reading to get more accurate data. By using the formulae, the standard deviation and relative standard deviation could be calculated. As the result, the lower the standard deviation, the higher the consistency of an instrument. Although the instrument may measure a given sample, the value might need to be altered due to various conditions and errors. Objectives The objective of the experiments was to; Calibrate a 10 mL volumetric pipette. Calibrate a 25 mL volumetric pipette. Calibrate a 100 mL volumetric flask. Calibrate a 50 mL measuring cylinder Introduction Volumetric glassware is used to accurately measure volumes. Despite all of the tools and instruments available for the use of measuring values of various data, it is impossible to measure the true value of anything. This experiment is intended to develop a person’s capacity to handle volumetric glassware. One must understand how to handle volumetric glassware to acquire  the best possible data from the equipment used in lab. Although the instrument may measure a given sample, the value might need to be altered due to various conditions. However, with practice and experience, we can reach very close to the true value, gaining the ability to measure with both high accuracy and precision. The objective of this experiment is to calibrate a 10mL burette and other volumetric glassware by calculating their correction values. By doing so, we can correct systematic errors caused by the burette’s or glassware’s values. A systematic error is an error in reading the scale when a physical quantity is being measured. Systematic errors are caused by the instrument, observer and surroundings. Another main type of error is random error. Random error is an error which occurs when the observer is reading the scale on the measuring instrument. Volumetric glassware is used to accurately measure volumes. In any given experiment, students may come across systematic errors or random errors. Random errors are not able to be corrected by a standard mean because they are not consistent. However, systematic errors are consistent and is able to be detected which allows students to correct the error that was found. So, using uncalibrated glassware will cause a systematic error. This error occurs because the volume reading given by the glassware is slightly different than the actual volume that is obtained in the glassware. In order to avoid systematic error, it important to calibrate the measuring instrument so that there is a standard value for zero which allows the measurement to be more accurate. Calibration of volumetric glassware such as burette is carried out by weighing the amount of water delivered. The temperature of the water used in the calibration must be known since the density of water changes. The purpose of this experiment is to investigate the measurement of the actual volume contents of volumetric glassware. If there is a slight variation in this instrument, it would cause systematic error and thus, the accuracy of results of an experiment or investigation would be affected. All volumetric glassware has marking on it. It is either being marked with TD or TC, which brings the meaning of ‘to deliver’ and ‘to contain’ respectively. For example, a pipette has a marking of TD, which means a pipette is marked  as a ‘to deliver’. Whereas, volumetric flask has TC as its marking, meaning it is marked as a ‘to contain’. A volumetric pipette & measuring cylinder can be calibrated by just weighing the water they deliver. As for volumetric flask, the weight of an empty flask is recorded. Next, weigh the flask after filling it with water to the mark. After that, it is crucial to convert the mass to volume. The water density at a t emperature will aid this process. The compliance of the Volume Occupied by 1.000g of Water Weigh in Air table is deemed necessary throughout the comparison. In order to obtain the true volume of volumetric glassware holds, this formula will be used. This experiment shall be repeated twice or more to enhance accuracy of the results obtained. Besides detecting systematic errors, this experiment would aid on the technique and understandings to the correct use of these equipments. Materials Transfer pipette, cleaning solution/detergent, beaker, thermometer, distilled water, top loading balance, 10ml volumetric pipette, 25mlvolumetric pipette, 100ml volumetric flask, 50ml measuring cylinder. Procedure 1) Calibration of a volumetric pipette (10ml and 25ml) a) Transfer pipette was obtained. The pipette was cleaned because distilled water does not drain uniformly. A cleaning solution or detergent was used to clean the pipette. b) An empty beaker was weighted. Then, water was filled in the beaker. The temperature was recorded at uniform intervals. c) The 10ml pipette was filled with distilled water until it reaches the calibration mark. d) Water was drained into another beaker e) The beaker filled with water was then weighted to find the mass of water delivered from the pipette. f) The following equation was used to convert mass to volume : Volume(actual) = (grams of water) x (volume of 1g of water in table1) g) Step a – f was repeated using 25ml pipette. 1) 2) Calibration of volumetric flask (100ml) a) A 100ml volumetric flask was cleaned and dried. b) The flask was weighted. Then, water was filled into the flask. Transfer pipette was used to remove the excess amount of water filled in the flask so that it exactly reach the calibration mark. c) The flask filled with water was weighted to find the mass of water contained in the flask. d) Mass of water was converted to volume using the equation above. 3) Calibration of a measuring cylinder (100ml) a) A 100ml measuring cylinder was cleaned and dried. b) The measuring cylinder was weighted. Then, water was filled into the measuring cylinder until it reached the calibration mark. Transfer pipette was also used to remove the excess water. c) The measuring cylinder filled with water was weighted to find the mass of water contained in the measuring cylinder. d) Mass of water was converted to volume using the same equation. Result and Discussion Result: a) Data 10mL pipette Trial 1 Trial 2 Trial 3 Mass of flask + water (g) 42.64 42.66 42.66 Mass of flask (g) 32.72 32.72 32.72 Mass of water (g) 9.92 9.94 9.94 Temperature (oC) 28 28 28 Actual volume (mL) 9.97 9.99 9.99 Average volume (mL) 9.98 Standard Deviation, 0.012 Relative standard deviation ,/ 0.001202 50mL pipette Trial 1 Trial 2 Trial 3 Mass of flask + water (g) 121.08 121.06 121.04 Mass of flask (g) 96.60 96.60 96.56 Mass of water (g) 24.48 24.46 24.48 Temperature (oC) 28 28 28 Actual volume (mL) 24.60 24.58 24.60 Average volume (mL) 24.59 Standard Deviation, 0.012 Relative standard deviation ,/ 0.00049 10mL pipette Trial 1 Trial 2 Trial 3 Mass of flask + water (g) 158.42 158.44 158.42 Mass of flask (g) 57.18 57.16 57.16 Mass of water (g) 101.24 101.28 101.26 Temperature (oC) 28 27 28 Actual volume (mL) 101.73 101.77 101.75 Average volume (mL) 101.75 Standard Deviation, 0.02 Relative standard deviation ,/ 0.000197 50mL measuring cylinder Trial 1 Trial 2 Trial 3 Mass of flask + water (g) 116.48 116.48 116.48 Mass of flask (g) 68.18 68.17 68.18 Mass of water (g) 48.30 48.31 48.30 Temperature (oC) 28 28 28 Actual volume (mL) 48.53 48.54 48.53 Average volume (mL) 48.53 Standard Deviation, 0.007 Relative standard deviation ,/ 0.000146 Discussion: According to the tables above, when using 10mL pipette, the actual volume delivered is 9.98mL and the standard deviation is 0.012. The lower the standard deviation, the higher the consistency of an instrument based in a physic’s book. Consistent measurements consist of readings that have little or no relative deviation among them. So, when the standard deviation is nearer to zero then this shows that the readings taken are consistent. In order to get a good accuracy, the experiments are done until trial 3. Temperature are remain consistent for all three trial for different glassware that 28 °C. This experiment expectation is that the glassware will be used to measure liquids at room temperature. Since liquids have a tendency to change volume (at the level of precision of calibrated instruments), then we want the liquid to be at the temperature we are most likely to use so that the calibration will have the most accuracy and we used water since it is thermal equilibrium in su rrounding. Another factor that may interrupt the reading is parallax error during the experiment is held. In order to avoid parallax error is the glassware must be weight for another two times. Every scale on the reading instrument must be read properly, it may reduce the fact. The eyes must be perpendicular to the reading scale on the same level as the bottom surface of the water meniscus to avoid parallax error. Besides, the weighing bottles are always being capped to avoid evaporation since it is important precaution. Conclusion Based on this experiment , we can conclude that this experiment are to study the calibration to measure the accuracy of volumetric glassware. This experiment also ensure the accuracy of the volumetric glassware for 10 ml and 25 ml pipette, 100 ml volumetric flask and 50ml measuring cylinder References * http://gula-gulakapassikecik.blogspot.com/2012/04/calibration-of-volumetric-glassware_24.html?m=1 * www.studymode.com * Lim Peng Chew, Lim Ching Chai, Nexus Bestari Physics, Sasbadi Sdn. Bhd. , 2013, Pg 18,19