Calculating Percent Error What is it Percent Error
- Slides: 13
Calculating Percent Error
What is it? ? Percent Error is used to determine the inaccuracy, in percentage, of a measured or estimated value, compared to an accepted value.
The Components of the Formula l l Estimated Value (Measured Value)- The value that has been derived from an experiment, or an estimated value. Actual Value (What you should have gotten!) - This value is the exact value excepted throughout the scientific community, or the value which is determined exact, at a later point in time.
The formula The Formula for Percent Error is a follows: l (EV – AV) X 100 = Percent Error AV Remember: EV= Estimated Value (measured value!) AV= Actual Value PS. We multiply by 100 to make the decimal a percent. l
What does it mean if the PE is positive or negative ? l l Negative if your measurement is too small Positive if your measurement is too big
Practice Problems l Johnny calculates from an experiment that he has 22. 7 grams of carbon. However, he should have gotten 21. 8 grams of carbon, which was the accepted value for this experiment. What was his percent error? l Remember: (EV-AV) X 100 = PE AV
Answer l (EV-AV) X 100 = PE AV (22. 7 - 21. 8) X 100 = PE 21. 8. 900 X 100 = PE 21. 8. 0413 X 100 = PE 4. 13 % = PE
More Practice l The actual value for the absorption of carbon is. 135. Steven calculated that absorption was. 235. What is the percent error in Steven’s experiment?
Answer l (EV-AV) X 100 = PE AV (. 235 -. 135) X 100 =PE. 135. 100 X 100 = PE. 135. 741 X 100 = PE 74. 1 % = PE
Additional practice 1. The boiling point of water is 100°C. During an experiment, water came to a boil at 97°C according to thermometer that was being used. What is the percent error of thermometer? answer 3. 0%
Additional practice 2. An experiment was conducted to find the mass of one mole of carbon atoms. The results of the experiment showed that a mole of carbon atoms had a mass of 15. 78 g. The accepted value of a mole of carbon atoms is 16. 00 grams. What is the percent error in this experiment? answer 1. 38%
Additional practice 3. An experiment performed to determine the density of lead yields a value of 10. 95 g/cm 3. The accepted value for the density of lead is 11. 342 g/cm 3. Find the percent error. answer 3. 46%
Additional practice 4. Find the percent error in a measurement of the boiling point of bromine if the laboratory figure is 40. 6°C and the accepted value is 59. 35°C. answer 31. 59 %
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