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CHEM 139: General Chemistry Prep Active Learning Questions, end of Chapter 2—(page 42a):

**1, 15**

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 .