Maximum Error 50cm3 Measuring Cylinder
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error'). Experimental uncertainty arises because of: Limits in the how exact the measuring apparatus is. This is the precision of the apparatus. Imperfections in experimental procedures. Judgements made by the operator. When can my results be said to be uncertainty of measuring cylinder precise? If you repeat a measurement several times and obtain values that are close together, your
Maximum Percentage Error Chemistry
results are said to be precise. If the same person obtains these close values, then the experimental procedure is repeatable. If a number of
Percentage Error Of Burette
different people carry out the same measuring procedure and the values are close the procedure is reproducible. What is a systematic error? A systematic error is one that is repeated in each measurement taken. If this is realised after the
100 Cm3 Measuring Cylinder Uncertainty
experimental work is done, it can be taken into account in any calculations. What are random errors? Even the most careful and experienced operator cannot avoid random errors. However, their effect can be reduced by carrying out a measurement many times (if the opportunity exists) and working out an average value. Let's look in more detail at 'built-in' uncertainty of some laboratory equipment... Some measurement uncertainties are given below: EquipmentMeasurement to the nearest: Balance (1 decimal place)0.08 g Balance (2 percentage error of 25cm3 pipette decimal place)0.008 g Balance (3 decimal place)0.0008 g Measuring Cylinder (25 cm3)0.5 cm3 Graduated Pipette (25 cm3, Grade B)0.04 cm3 Burette (50 cm3, Grade B)0.08 cm3 Volumetric Flask (250 cm3, Grade B)0.2 cm3 Stopwatch (digital)0.01 s Calculating the percentage uncertainty (often called percentage error) ... Now try calculating the following percentage uncertainties... 1.00 g on a 2 decimal place balance 10.00 g on a 2 decimal place balance 1.00 g on a 3 decimal place balance 10 cm3 in a 25 cm3 measuring cylinder 25 cm3 in a 25 cm3 measuring cylinder 25 cm3 in a 25 cm3 graduated pipette (Grade B) 25 cm3 in a 50 cm3 burette (Grade B) 250 cm3 in a 250 cm3 volumetric flask (Grade B) 50 s on a digital stopwatch 8% 0.8% 0.08% 5% 2% 0.16% 0.32% 0.08% 0.02% Comparing uncertainties like those calculated above 'might' help you to decide which stage in an experimental procedure is likely to contribute most to the overall experimental uncertainty. How about thermometers...? Spirit filled thermometers are regularly used in college laboratories. They are often more precise than accurate. It is quite easy to read a thermometer to the nearest 0.2 °C. However, the overall calibration can be out by a degree or more. For example, for a thermometer reading 43 °C, if it is not of high quality the real temperature could be as high as 44 °C or as low as 42 °C. Ar
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