Name ___________________________________ Date _______________
PRECISION, ACCURACY AND SIGNIFICANT DIGITS
IB Chemistry HL Juniors 5092-5093
1. Three students each use the same meter stick to measure the length of a room. The actual room
length is 11.25 meters and they report the following measurements:
Student A’s measurement:
Student B’s measurement:
Student C’s measurement:
10.94 meters
10.93 meters
10.93 meters
A. Describe the precision. __________________________________________________
B. Describe the accuracy. __________________________________________________
C. How many Sig Figs in each measurement? __________________________________
D. How many certain digits in each measurement? ______________________________
2. The boiling point of pure water at sea level is known to be 100.0ºC. Using a new thermometer, a
student measures the boiling point of pure water (at se level) three times. Each time the thermometer
reads 98.6ºC.
A. Describe the precision. __________________________________________________
B. Describe the accuracy. __________________________________________________
C. How many Sig Figs in each measurement? __________________________________
D. What is the percent error? _______________________________________________
3. A standard 20.00 g mass is used to check the accuracy of a laboratory balance. The balance
indicates a mass of 19.81 g on each of 4 measurements when the standard mass is measured.
A. Describe the accuracy of the balance. _______________________________________
B. Describe the precision of the balance. _______________________________________
C. What is the percent error of this measurement? ________________________________
4. Five students each weigh the same object on the same balance. The actual mass of the object is
known to be 3.135 g. Their results are:
Student 1:
3.137 g
Student 4:
2.832 g
Student 2:
3.137 g
Student 5:
3.136 g
Student 3:
3.134 g
A. Describe the precision of the balance. _______________________________________
B. Describe the accuracy of the balance. _______________________________________
C. Comment on the 5 students: _______________________________________________
D. How many sig figs are in these values? ______________________________________
5. How many significant digits are in the following?
a. 0.0789 m __________
d. 2090 cm __________
b. 200010 g __________
e. 49.00 L ___________
c. 105.30 mL _________
f. 300 cm3 ___________
6. Calculate the following using correct significant digits:
a. 27.40 – 3.7
d. (4.75 – 3.89)/4.75
b. 300 + 2.5
e. 200.0 x 28 x 4.18
c. 8.69 – 4.29
f. (252 x 3.1) / 80
7. Convert the following metric values:
a. 278 mm to km
d. 24 Mg to cg
b. 23.5 hL to dL
e. 374 mg to μg
c. 5.89 nm to dam
f. 49.6 nm to μm