Chapter 1 Suggested Homework Answers
Problems: 10, 18, 24, 30, 34, 36, 38, 40, 42, 46, 48, 61, 68, 70
10. (a) Air is a homogeneous mixture of various gases such as nitrogen, oxygen, and carbon dioxide.
(b) Tomato juice is a heterogeneous mixture.
(c) Iodine crystals are a pure substance.
(d) Sand is a pure substance.
18. The physical properties of zinc described in the problem are: silver-gray color; melts at 420°C; hardness; and its density. The chemical properties are: when zinc granules are added to dilute sulfuric acid, hydrogen gas is given off and the metal dissolves; and the reaction of zinc with oxygen gas at elevated temperatures to form zinc oxide.
24. (a) Using the conversion factor: 1 cL = 10-2 L:
(b) Using the conversion factor: 1 ms = 10-6 s
(c) Using the conversion factor: 1 mm = 10-3 m
(d) Using the conversion factor: 1 mm3 = 10-9 m3 [ (1 mm)3 = (10-3 m)3] (Be careful with cubic lengths!!)
(e) Using the conversion factors: 1 kg = 103 g and 1 mg = 10-6 g
(f) Using the conversion factor: 1 ng = 10-9 g
(g) Using the conversion factors: 1 fs = 10-15 s and 1 ms = 10-6 s
30. (a) Given the volume of 25.0 mL and the mass of 21.95 g, calculate the density of the liquid in the bottle:
This value is in agreement with the literature value of 0.8787 g/mL at 15°C.
(b) Given a mass of 15.0 g and a density of 0.7781 g/mL, calculate the volume of 15.0 g of cyclohexane:
(c) Calculate the volume of the lead sphere of radius, 5.0 cm:
Given the density of 11.34 g/cm3 and the volume calculated above, the mass of the lead sphere is equal to:
34. (a) Converting 87°F to °C:
(b) Converting 25°C to K and °F:
(c) Converting 175°F to °C and K
(d) Converting 755°C to °F and to K:
(e) Converting –248.6°C to Kelvin:
Converting –246.1°C to Kelvin:
36. (a) The mass of a 32 oz. can of coffee is a measured value. It is not exact.
(b) The number of students in your chemistry class is a counting number. It is exact.
(c) The temperature of the surface of the sun is a measured value. It is not exact.
(d) The mass of a postage stamp is a measured value. It is not exact.
(e) The number of milliliters in a cubic meter of water is a metric definition. It is exact.
(f) The average height of students in your school is an average of measured values. It is not exact.
38. (a) 3.7745 km has 5 significant figures.
(b) 205 m2 has 3 significant figures.
(c) 1.700 cm has 4 significant figures.
(d) 350.0 K has 4 significant figures.
(e) 307.080 g has 6 significant figures.
40. (a) 7926.381 mi. rounded to 3 significant figures is 7.93 × 103 mi. in scientific notation.
(b) 40,008 km rounded to 4 significant figures is 4.001 × 104 km in scientific notation.
42. (a) The result of the division inside the parentheses is reported to 2 significant figures:
In the subtraction, because the second number has ends in the hundred’s digit, the result must be cut off at the hundred’s digit.
(b) Since the first number in the subtraction ends at the ten-thousand’s digit, the result of the subtraction must be cut off at the ten-thousand’s digit which leaves the first number essentially unchanged (because 1.200 × 10-3 is much, much smaller than 285.3 × 105). The result of the multiplication is reported to 4 significant figures because 285.3 × 105 has 4 significant figures. The answer is converted to scientific notation.
(c) The result of the multiplication inside the parentheses is reported to 3 significant figures because both of the numbers have 3 significant figures. The result of the subtraction inside the square brackets is cut off at the singles digit since both numbers end in the singles digit. Finally, the result of the multiplication is reported to 3 significant figures.
46. (a) Use the following conversion factors when converting m/s to km/hr: 1000 m = 1 km, 3600 s = 1 hr
(b) Use the following conversion factors to convert ft. into m: 3 ft. = 1 yd, 1 m = 1.0936 yd
(c) Use the following conversion to convert m3 to L: 1 L = 10-3 m3
(d) Convert the cholesterol level of 232 mg/100 mL (232 mg per 100 mL) to mg/L using the conversion 1000 mL = 1 L:
Multiply this by the volume of blood of 5.2 L to obtain the total mg of cholesterol:
Use the conversion 1000 mg = 1 g to convert this to grams of cholesterol:
48. (a) Use the following conversions to convert in. to mm: 2.54 cm = 1 in, exactly, 100 cm = 1 m, 1000 mm = 1 m
(b) Use the following conversions to convert qt to mL: 1 L = 1.0567 qt and 1000 mL = 1 L
(c) Use the following conversions to convert mm/s to km/hr: 1 mm = 10-6 m, 1000 m = 1 km, 3600 s = 1 hr
(d) Use the following conversion to convert yd3 to m3: 1.3079 yd3 = 1 m3 [(1.0936 yd)3 = (1 m)3] Be careful with cubic lengths!!
(e) Use the following conversion to convert $/lb to $/kg: 1 kg = 2.2046 lb
(f) Use the following conversions to convert lb/ft3 to g/mL: 1 lb = 453.59 g, 1728 in3 = 1 ft3 [(12 in)3 = (1 ft)3], 1 in3 = 16.4 cm3, 1 cm3 = 1 mL
61. (a) For set 1, the average percentage is equal to:
For set 2, the average percentage is equal to:
Set 1 is the most accurate since the average percentage of 22.51% is closer to the true value of 22.52% than the average percentage of set 2 of 22.61%.
(b) Calculating the deviations from the average percentage for the first set and then taking the average deviation:
The average deviation for set 1 is 0.07%/3 = 0.023%
Calculating the deviations for set 2:
The average deviation for set 2 is also 0.07%/3 = 0.023%. Since both sets have the same average deviation, both sets are equally precise. (The set with the lower average deviation would be the more precise).
68. (a) Use the following conversion to convert lb. to g: 453.56 g = 1 lb
(b) Calculate the volume of sodium hydroxide from the mass and its density:
Use the following conversions to convert cm3 to km3 (be careful with cubic lengths!!): 106 cm3 = 1 m3, 109 m3 = 1 km3
70. Calculate the mass of battery acid from the volume and the density:
Take 38.1% of this to calculate the mass of sulfuric acid:
