Cliffs AP Chemistry, 3rd Edition

Samples: Multiple-Choice Questions

1. A popular Bourbon whiskey is listed as being “92 Proof.” The liquor industry defines
   “Proof” as being twice the volume percentage of alcohol in a blend. Ethanol (drinking
   alcohol) has the structural formula CH 3 CH 2 OH (MW = 46 g/mol). The density of ethanol
   is 0.79 g/mL. How many liters of whiskey must one have in order to have 50. moles of
   carbon?

A. 0.80 liters

B. 1.6 liters

C. 3.2 liters

D. 4.0 liters

E. 6.4 liters

Answer: C

Step 1: Write down an equals sign (=).

Step 2: To the right of the equals sign, write down the units you want the answer to be in.
Examination of the problem reveals that you want your answers in “liters of whiskey,” so you
have

= liters of whiskey

Step 3: Begin the problem with the item you are limited to. In this case, it is 50. moles of car-
bon — no more, no less. Place the 50. moles of carbon over 1.

. moles of carbon liters of whiskey
1

(^50) =
Step 4: Get rid of the units “moles of carbon” by placing them in the denominator of the next
factor. What do you know about moles of carbon? There are 2 moles of carbon in each mole of
ethanol.

. moles of carbon
moles carbon

mole ethanol liters of whiskey

1

50

2

#^1 =

Step 5: Continue in this fashion, getting rid of unwanted units until you are left in the units you
desire. At that point, stop and do the calculations.

. moles carbon
moles carbon

mole ethanol

mole ethanol

grams ethanol

1

50

2

1

1

46

##

. g ethanol.

mL ethanol

mL ethanol

mL whiskey

mL whiskey

L whiskey

079 L whiskey

1

92

200

10

1

### 3 = 32

Part II: Specific Topics