PERCENT ERROR WORKSHEET

Name __________________________Date _________________Period______

1.  John uses his thermometer and finds the boiling point of ethyl alcohol to be

75o C.  He looks in a reference book and finds that the actual boiling point of ethyl alcohol is 78oC.  What is his percent error? (-3.8 %)

2.  Anna weighed an object on her balance and recorded a mass of 24.2 grams.

Her teacher told her that there was obviously something wrong with her balance because it was giving her a reading which was 33.2% too high.  What was the actual mass of the object? (18.2 ºC)

3.  An AP student got a lab report back with “-4.5% error” written in red on it.  He

had determined the boiling point of an unknown liquid to be 45o C.  What is the correct boiling point of his unknown liquid? (47.1 ºC)

4.  The density of water at 4oC is known to be 1.00 g/mL.  Kim experimentally

found the density of water to be 1.085 g/mL.  What is her percent error?  (8.5% error)

5.  The Handbook of Chemistry and Physics lists the density of a certain liquid to

be 0.7988 g/mL.  Fred experimentally finds this liquid to have a density of 0.7914 g/mL.  The teacher allows up to +/- 0.500% error to make an “A” on the lab.  Did Fred make an “A”?  Prove your answer.  (no, he didn’t; his % error is –0.93%)

6.  An object has a mass of 35.0 grams.  On Huey’s balance, it weighs 34.92

grams.  What is the percent error of his balance?  (-0.22%)

7.  Florence measured the volume of a cylinder and determined it to be 54.5 cm3.

The teacher told her that she was 4.65% too high in her determination of the volume.  What is the actual volume of the cylinder?  (52.1 cm3 or 5.21 X 101 cm3)

8.  Barry Um gets a paper back in lab with “-2.77% error” written on it.  He had

found the mass of an object to be 100.3 grams.  What should he have found as the mass of the object?  (103 grams)

9.  After lab, all of Henry’s friends looked at his data and laughed and laughed.

They told him that he was 31.2% too low in the boiling point he had just recorded.  He had recorded a boiling point of 50o C on his data sheet.  What is the correct boiling point of the liquid he was working with in lab?  (72.7oC)