Page 36 - Theory and Problems of BEGINNING CHEMISTRY

CHAP. 2] MATHEMATICAL METHODS IN CHEMISTRY 25

Ans. 64 oz gold 36 oz other metal 36 oz other metal
100 oz total 100 oz total 64 oz gold
or the reciprocals of these:
100 oz total 100 oz total 64 oz gold
64 oz gold 36 oz other metal 36 oz other metal

2.6. Calculate the number of children in a second-grade class of 18 girls in which there are 60% girls.
100 children

Ans. 18 girls = 30 children
60 girls
2.7. If pistachio nuts cost $6.00 per pound. (a) How many pounds of nuts can be bought for $21.00? (b)How
much does 2.43 pounds of nuts cost?

1 pound
Ans. (a)21.00 dollars = 3.50 pounds
6.00 dollars
6.00 dollars

(b)2.43 pounds = 14.58 dollars
1 pound
2.8. If 44% of a certain class is female, how large is the class if there are 77 females?
100 people

Ans. 77 females = 175 people
44 females
2.9. If income tax for a certain student is 14%, how much gross pay does that student need to earn to be able
to keep $425? (Assume no other deductions.)
Ans. If 14% goes to tax, 100% − 14% = 86% is kept.

100 dollars gross
425 dollars kept = 494.19 dollars gross
86 dollars kept
2.10. Commercial sulfuric acid solution is 96.0% H 2 SO 4 in water. How many grams of H 2 SO 4 are there in
175 g of the commercial solution?

96.0gH 2 SO 4
Ans. 175 g solution = 168gH 2 SO 4
100 g solution
METRIC SYSTEM
2.11. (a) Is there a unit “ounce” that means a weight and another that means a volume? (b) Is there a metric
unit that means both weight and volume? (c) What is the difference in weight between an ounce of gold
and an ounce of lead?
Ans. (a) Yes, 16 fluid oz = 1 pint, 16 oz avoirdupois = 1 pound, and 12 oz Troy = 1 pound Troy.
(b) No.
(c) Gold is measured in Troy ounces, and lead is measured in avoirdupois ounces.

2.12. Is there a difference between a U.S. gallon and an imperial gallon?
Ans. They are two different units despite both having the word gallon in their names. The U.S. gallon is equal to
3.7853 L; the imperial gallon is equal to 4.5460 L.

2.13. There are nickels in one container and pennies in another. Each container holds the same amount of
money. (a) Which container holds more coins? (b) In which container is each coin more valuable?
Ans. The more valuable the coin, the fewer are required to make a certain amount of money. The nickels are each
more valuable, so there are more pennies.