# Unit Conversions and Significant Figures Problem Set

This problem set was developed by S.E. Van Bramer for Chemistry 145 at Widener University.

1. Conversions: Express the following in the units asked for:
1. Speed of light, 3x108 m s-1, in miles per hour and meters/sec.
2. Speed of sound, 740 mph, in kilometers per hour and meters/sec.
3. Length of a C-C bond in diamond, 1.54452 Å, in cm, m, and inches (watch significant figures on this one)
4. Temperature
1. LN2, -195 C, in F and K
2. Body Temp, 98 F, in C and K
3. Paper Flashpoint, 450 F, in C and K
4. Derive Conversion for F to C based on freezing and boiling point of water.

2. What is the volume of object that is 83.6 cm long, 10.62 cm wide, and 1.2 inches thick? What is the volume after 5.74 cm is cut off from the long edge?

3. Solve the following problems and express the results with the correct number of significant figures.

1. 3.894 x 2.16 =
2. 2.96 + 8.1 + 5.0214 =
3. 2.17 + 4.32 + 401.278 + 21.826 =
4. 485 ÷ 9.231=
5. 2.46 x 2 =
6. 9.146 - 9.137 =
7. (5.12 x 104) * (6.8726 x 10-9) =

4. The mass of the sun is 1.989x1030 kg and the radius is 696000 km. More on the sun. What is the average density of the sun in the following units:
1. kg/km3 =
2. kg/m3 =
3. kg/cm3 =
4. g/cm3 =

5. In the opening scenes of the movie Raiders of the Lost Ark, Indiana Jones tries to remove a gold idol from a booby-trapped pedestal. He replaces the idol with a bag of sand of approximately equal volume. (Density of gold = 19.32 g/cm3; density of sand 3 g/cm3.) {from Zumdahl, Chemistry, Saunders (1994).

1. Did he have a reasonable chance of not activating the mass-sensitive booby trap?

2. In a later scene he and an unscrupulous guide play catch with the idol. Assume that the volume of the idol is about 1.0 L. If it were solid gold, what mass would the idol have? Is playing catch with it plausible?

6. The world record for the hundred meter dash is (ref: USA Track and Field):
• Men 9.79 Maurice Greene (USA)
• Women 10.49 Florence Griffith-Joyner (USA)

1. What is the average speed in m/s
2. What is the average speed in km/h
3. What is the average speed in ft/s
4. What is the average speed in mi/h?
5. At this speed, how long would it take to run 1.00 x 102 yards?

7. The mercury concentration in a polluted lake is 0.0125 µg Hg/L, what is the total mass in kilograms of mercury in the lake if the lake is approximately circular with a diameter of 10 miles and an average depth of 50 ft?

Please send comments or suggestions to svanbram@science.widener.edu

Scott Van Bramer
Department of Chemistry
Widener University
Chester, PA 19013