Page 46 - Theory and Problems of BEGINNING CHEMISTRY

CHAP. 2] MATHEMATICAL METHODS IN CHEMISTRY 35

(g) Change 242.4 mL to quarts (U.S.) (i) Change 6.49 kg to ounces
(h) Change 13.71 ft to meters (j) Change 433 km to miles

2.54 cm
Ans. (a)4.22 in. = 10.7cm
1in.

2.20 lb
(b)2.35 kg = 5.17 lb
1kg

1.06 qt 32 oz
(c) 6.13 L = 208 oz
1L 1qt
1.0kg 1000 g

3
(d)21.7lb = 9860 g = 9.86 × 10 g
2.2lb 1kg

60.0mi 1760 yd 36 in. 1m 1h 26.8m
(e) =
h 1mi 1yd 39.37 in. 3600 s s
2
2.54 cm

(f) 3.50 in. 2 = 22.6cm 2
1in.

1L 1.06 qt
(g) 242.4mL = 0.257 qt
1000 mL 1L

12 in. 2.54 cm 1m
(h)13.71 ft = 4.18 m
1ft 1in. 100 cm
2.2lb 16 oz

(i) 6.49 kg = 228 oz
1kg 1lb
0.621 mi

(j) 433 km = 269 mi
1km
2.79. Round the atomic masses (found in the periodic table) of the first 20 elements to three significant digits each.
Ans. H 1.01 C 12.0 Na 23.0 S 32.1
He 4.00 N 14.0 Mg 24.3 Cl 35.5
Li 6.94 O 16.0 Al 27.0 Ar 39.9
Be 9.01 F 19.0 Si 28.1 K 39.1
B 10.8 Ne 20.2 P 31.0 Ca 40.1
2.80. What is wrong with the following problem? Change 125 g to milliliters.
Ans. You cannot change a mass to a volume (unless you have a value for density).
2.81. What is the volume of 125 g of water?
Ans. The one density that you must know is that of water, about 1.00 g/mL.
1mL

125 g = 125 mL
1.00 g
2.82. Express, in standard exponential notation, the number of
(a) grams in 7.65 ng (e) milliliters in 3.21 L
(b) meters in 8.76 dm (f) grams in 4.32 kg
(c) kilograms in 9.87 mg (g) centimeters in 5.43 m
(d) liters in 6.54 mL

3
Ans. (a) 7.65 × 10 −9 g (e) 3.21 × 10 mL
3
(b) 8.76 × 10 −1 m (f) 4.32 × 10 g
2
(c) 9.87 × 10 −6 kg (g) 5.43 × 10 cm
(d) 6.54 × 10 −3 L