CHEM 139: General Chemistry Prep Active Learning Questions, end of Chapter 2—(page 42a):
Setting up Conversion Problems 1)
Find an equality
expressing the same quantity in two different units—the unit matching your measurement and the desired unit, or 1 step closer to. Every equality (x = y) generates two conversion factors (x/y = 1; y/x = 1). 2)
Multiply your measurement
by the conversion factor which cancels the original unit. Repeat until your measurement is expressed in the desired units. Does your answer make sense? Check significant figures! Example: A book masses 0.550 lb. What is this mass in grams? 1 kg = 2.205 lb. Answer: The second equality needed is 1000 g = 1 kg. 0.550 lb x (1 kg/2.205 lb) x (1000 g/1 kg) = 249 g Extra conversion problems: convert each of the following as indicated. a) 8956 msec to min b) 2610 ft 2 to m 2 c) 0.0000068 m 3 to ml d) 0.072 lb/cm 3 to mg/L e) On average, the moon takes 27 d, 7 hr, and 43.2 min to make a complete circuit around the Earth. Express this time in hours. f) A diamond is made of pure carbon. The distance between any two neighboring atoms in a diamond is 1.54 angstroms (A). (1 A = 10 -10 m) What is this distance in inches? g) If an audiotape playing at a speed of 1.875 in./s takes 45.0 min to play through one side, what is the length of the tape in feet? In meters? h) The average density of whole milk is 1.034 g/cm 3 . What is its density in lb/gal? i) What is the mass of a ceramic vase that displaces 48 ml of water when immersed in a water bath? The density of the ceramic is 4.71 g/cm 3 . j) What is the volume of a small iceberg massing 6.5 x 10 4 kg? What would be the volume of water obtained from the iceberg, were it to melt completely? The density of ice is 0.917 g/cm 3 , and the density of water is 1.0000g/cm 3 .