Basic Laboratory Technique
Basic Laboratory Technique
CHEMICALS AND APPARATUS
Distilled water, analytical balance,burette, pipette(25ml), volumetric flask(25ml), conicalflask, beaker (50ml), and thermometer.
1. Calibration of volumetric flask
(a) A 25ml volumetric flask was cleaned and dried then, accurately weighed using analytical balance. (b) The volumetric flask was filled with distilled water and weighed again. (c) The temperature of the distilled water was recorded.
(d) From Table 1.1, the actual volume of the volumetric flask was determined.
2. Calibration of pipette
(a) A 50ml beaker was cleaned and dried then, accurately weighed using analytical balance. (b) A 25ml pipette was cleaned and rinsed with distilled water. (c) The pipette was filled with distilled water using the procedures that have been discussed in the introduction part. (d) The distilled water was drained into the beaker and weighed again. The weight was recorded (e) Step 1-4 was repeated one more time and the temperature of the distilled water was recorded. (f) From Table 1.1,the actual volume of the pipette was determined
3. Calibration of burette
A 50ml beaker was cleaned and dried then, accurately weighed using analytical balance. A burette was cleaned and rinsed using distilled water and the burette was filled with water until it reached the zero mark 5ml of the water was drained from the burette into the beaker and weighed. The weight was recorded. Step (c) was repeated by draining water from the burette until the following burette reading becomes 10ml, 15ml, and 20 ml. (Each time 5ml distilled water was added from the burette). The weight of the water and the beaker was recorded every time after adding 5ml of distilled water. From Table 1.1, the actual volume for every addition of 5ml of distilled water was determined.
The results that are obtained are just like the prediction made although there are a few errors. Fromthe test make for the calibration of volumetric flask, the data obtained for the volumetric flask’s mass is 22.3369g. When the water was added, the mass for both volumetric flask and the water contained in it is 47.030. As the mass of the volumetric flask had been subtracted, the mass of the water is 24.6661 while its temperature is 31˚c. Therefore, from the table 1.1, it’s density of water is 1.0053g/ml.therefore, the results obtained was accepted.
For the experiment made for the calibration of pipette, the data resulted that the mass of the beaker taken were 35.6142g for trial (i) and 35.5164g for trial (ii). As the water added into the beaker, the data becomes 60.5456g and 60.2812g for trial (i) and (ii) respectively. When the mass of the beaker was subtracted, it’s turn out that the mass of the water for trial(i) and (ii) are 24.9314g and 4.7648g. Then, when the temperature of the water taken from both trial, it’s has the same temperature which is 29˚c.from table 1.1, it shown that the density of the of the water is 1.0050g/ml.Again,the results was accepted.
For the experiment of the calibration of burette, the results obtained are indefinite with the standard reading of burette.For the first reading which is 5ml, the last data obtained is 4.40ml. This data is not even close to the reading of the burette that had been fixed at the beginning of the experiment although it had been round off. This event occurred as there were some random error had been caused by the experimenters as they are not keep their eyes levelat the same level of the meniscus. There are maybe also caused by systemic error which is also the experimenters’ careless attitude as they are not checking the apparatus carefully whether it still can be use or not.
Thus, with the experiments made for the calibration of volumetric flask, pipette and burette, the experimenters had learn about the qualitative and quantitative aspect of this common laboratory equipment as they had measured and recorded the volume of these apparatus. These experiments also had taught and exposed them to the factor that had affected the accuracy of an experiments which are systemic errors and systemic errors that can occurred in any experiment if they do not take the precaution seriously.
1. How do you overcome or reduce the problem of random error and systematic error while doing an experiment? A systematic error is a reproducible inaccuracy with a nonzero mean or an improper calibration of the measuring instrument. If the measuring instrument is not at zero prior to measuring the object you will get a systematic error which, is a value either always higher or always lower than the actual value of the object.It can be avoided by ensuring that the measuring equipment is not flawed.
Random error are statistical fluctuation in the measured data due to the precision limitations of the measurement device.This means your result is accurate but not precise. The only way to minimize random error is to repeat the experiment more times to get a better average.
2. In what situation do you use a volumetric flask,conical flask, pipette and graduated cylinder? Volumetric flasks are specially designed containers for very accurate mixing and diluting. Like volumetric pipettes, volumetric flasks are designed to measure one volume only. The long neck makes it easy to determine when the final volume has been reached.
Conical flask are also called Erlenmeyer flask. The primary use for Erlenmeyer flasks is in mixing chemicals. Because the sides of Erlenmeyer flasks are slanted and the mouth is narrow, mixing reagent liquids can be accomplished by swirling without fear of spilling the contents. The advantage of this type of flask is that special stirring equipment (such as a magnetic stirrer) is not needed. The volumes stamped on the side are approximate and accurate to within about 5%.
Graduated cylinders are useful for measuring liquid volumes to within about 1%. They are for general purpose use, but not for quantities analysis. Although not nearly as accurate as pipettes, graduated cylinders have an advantage in that they require much less technique to use. This allows for more reproducible results for those who are unfamiliar with proper laboratory techniques.
Basically, pipets are specially designed and calibrated glass tubes used for accurately transferring small volumes of solution (usually 50 mL or less) from one container to another. Pipets are available in a variety of types and sizes, for many different uses.
3. Explain how to read a burette. What are the factors to be considered when using a burette?
To read a burette, the experimenter must remember that the numbers starts at 0.00 on the top and go to 25.00 at the bottom. He must read the liquid level using the bottom of the meniscus which is a curved surfaces that existed at the top of the liquid level.
When using a burette, there are some factors to be considered. First and foremost,. He have to test the burette with distilled water to ensure that there are no liquid adheres to the side. Besides, hemust keep his eyes level at the same level of the meniscus to avoid parallax in reading the volumes. Then, he should make sure that the titrant is well mixed before using by shaking the bottle well.in addition, he must make sure that there is no bubbles inside the burette. Last but not least,you must rinsed out the burette with distilled water when finished and store inverted or filled with distilled water and a cap to prevent dust from entering
AnisahRafidahAhmad,NurNasulhahKasim,RizanaYusof;(2012);principle of general chemistry; The factors should be considered when using a burette;4Julai 2015, https://answers.yahoo.com/question/index?qid=20130706161735AAlSnHA
Systemic errors and random error;6Julai 2015,
The function of laboratory;s apparatus;4 Julai 2015
chemistry laboratory’ apparatus;4 Julai 2015
University/College: University of Chicago
Type of paper: Thesis/Dissertation Chapter
Date: 26 September 2016
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