Selected Exercise Chemistry_The Central Science
Introduction: Matter and Measurement
1.1 Which of the following figures represents (a) a pure element, (b) a mixture of two elements, (c) a pure compound, (d) a mixture of an element and a compound? (More than one picture might fit each description.) [Section 1.2]
(a) What is the length of the pencil in the following figure if the scale reads in centimeters? How many significant figures are there in this measurement? (b) An oven thermometer with a circular scale reading degrees Fahrenheit is shown. What temperature does the scale indicate? How many significant figures are in the measurement? [Section 1.5]
1.13 Give the chemical symbol or name for the following elements, as appropriate: (a) sulfur, (b) magnesium, (c) potassium, (d) chlorine, (e) copper, (f) F, (g) Ni, (h) Na, (i) Al, (j) Si.
1.15 A solid white substance A is heated strongly in the absence of air. It decomposes to form a new white substance B and a gas C. The gas has exactly the same properties as the product obtained when carbon is burned in an excess of oxygen. Based on these observations, can we determine whether solids A and B and the gas C are elements or compounds? Explain your conclusions for each substance.
1.23 What exponential notation do the following abbreviations represent: (a) d, (b) c, (c) f, (d) , (e) M, (f) k, (g) n, (h) m, (i) p?
1.25 Make the following conversions: (a) 62F to C, (b) 216.7C to F, (c) 233C to K, (d) 315 K to F, (e) 2500 F to K.
1.33 Indicate which of the following are exact numbers: (a) the mass of a paper clip, (b) the surface area of a dime, (c) the number of inches in a mile, (d) the number of ounces in a pound, (e) the number of microseconds in a week, (f) the number of pages in this book.
1.35 What is the number of significant figures in each of the following measured quantities? (a) 358 kg, (b) 0.054 s, (c) 6.3050 cm, (d) 0.0105 L, (e) 7.0500 x 10-3 m3.
1.37 Round each of the following numbers to four significant figures, and express the result in standard exponential notation: (a) 102.53070, (b) 656,980, (c) 0.008543210, (d) 0.000257870, (e) -0.0357202.
1.39 Carry out the following operations, and express the answers with the appropriate number of significant figures.
(a) 12.0550 + 9.05
(b) 257.2 - 19.789
(c) (6.21 x 103) (0.1 050)
1.41 Using your knowledge of metric units, English units, and the information on the back inside cover, write down the conversion factors needed to convert (a) mm to nm, (b) mg to kg, (c) km to ft, (d) in.3 to cm3.
1.43 Perform the following conversions: (a) 0.076 L to mL, (b) 5.0 x 10-8 m to nm, (c) 6.88 x 105 ns to s, (d) 0.50 lb to g, (e) 1.55 kg/m3 to g/L, (f) 5.850 gal/hr to L/s.
1.45 Perform the following conversions: (a) 5.00 days to s, (b) 0.0550 mi to m, (c) $1.89/gal to dollars per liter, (d) 0.510 in./ms to km/hr, (e) 22.50 gal/min to L/s, (f) 0.02500 ft3 to cm3
1.49 The density of air at ordinary atmospheric pressure and 25C is 1.19 g/L. What is the mass, in kilograms, of the air in a room that measures 12.5 x 15.5 x 8.0 ft?
1.55 What is meant by the terms composition and structure when referring to matter?
1.61 What type of quantity (for example, length, volume, density) do the following units indicate: (a) mL, (b) cm2, (c) mm3, (d) mg/L, (e) ps, (f) nm, (g) K?
1.70 A 32.65 g sample of a solid is placed in a flask. Toluene, in which the solid is insoluble, is added to the flask so that the total volume of solid and liquid together is 50.00 mL. The solid and toluene together weigh 58.58 g. The density of toluene at the temperature of the experiment is 0.864 g/mL. What is the density of the solid?
Kimia, Matematika, Fisika, Geofisika, Geologi
1.4 Three spheres of equal size are composed of aluminum (density = 2.70 g/cm3), silver (density = 10.49 g/cm3), and nickel (density = 8.90 g/cm3). List the spheres from lightest to heaviest.
1.8 (a) How many significant figures should be reported for the volume of the metal bar shown below? (b) If the mass of the bar is 104.7 g, how many significant figures should be reported when its density is calculated using the calculated volume? [Section 1.5]
1.11 Classify each of the following as a pure substance or a mixture. If a mixture, indicate whether it is homogeneous or heterogeneous: (c) magnesium, (d) gasoline.
1.17 In the process of attempting to characterize a substance, a chemist makes the following observations: The substance is a silvery white, lustrous metal. It melts at 649C and boils at 1105C. Its density at 20C is 1.738 g/cm3. The substance burns in air, producing an intense white light. It reacts with chlorine to give a brittle white solid. The substance can be pounded into thin sheets or drawn into wires. It is a good conductor of electricity. Which of these characteristics are physical properties, and which are chemical properties?
1.19 Label each of the following as either a physical process or a chemical process: (a) corrosion of aluminum metal.
1.21 Suggest a method of separating each of the following mixtures into two components: (b) iron and sulfur.
1.27 (a) A sample of carbon tetrachloride, a liquid once used in dry cleaning, has a mass of 39.73 g and a volume of 25.0 mLat 25 'C. What is its density at this temperature? Will carbon tetrachloride float on water? (Materials that are Jess dense than water will float.) (b) The density of platinum is 21.45 g/cm3 at 20 C. Calculate the mass of 75.00 cm3 of platinum at this temperature. (c) The density of magnesium is 1.738 g/cm3 at 20 C. What is the volume of 87.50 g of this metal at this temperature?
1.29 (a) To identify a liquid substance, a student determined its density. Using a graduated cylinder, she measured out a 45-mL sample of the substance. She then measured the mass of the sample, finding that it weighed 38.5 g. She knew that the substance had to be either isopropyl alcohol (density 0.785 g/mL) or toluene (density 0.866 /mL). What are the calculated density and the probable identity of the substance? (b) An experiment requires 45.0 g of ethylene glycol, a liquid whose density is 1.114 g/mL. Rather than weigh the sample on a balance, a chemist chooses to dispense the liquid using a graduated cylinder. What volume of the liquid should he use? (c) A cubic piece of metal measures 5.00 cm on each edge. If the metal is nickel, whose density is 8.90 g/cm3, what is the mass of the cube?
1.31 Gold can be hammered into extremely thin sheets called gold leaf. If a 200-mg piece of gold (density = 19.32 g/cm3) is hammered into a sheet measuring 2.4 x 1.0 ft, what is the average thickness of the sheet in meters? How might the thickness be expressed without exponential notation, using an appropriate metric prefix?
1.47 (c) If an automobile is able to travel 254 mi on 11.2 gal of gasoline, what is the gas mileage in km/L?
1.51 By using estimation techniques, arrange these items in order from shortest to longest: a 57 cm length of string, a 14 in. long shoe, and a 1.1 m length of pipe.
1.53 The Morgan silver dollar has a mass of 26.73 g. By law, it was required to contain 90% silver, with the remainder being copper. (a) When the coin was minted in the late 1800s, silver was worth $1.18 per troy ounce (31.1 g). At this price, what is the value of the silver in the silver dollar? (b) Today, silver sells for about $13.25 per troy ounce. How many Morgan silver dollars are required to obtain $25.00 worth of pure silver?
1.64 The US quarter has a mass of 5.67 g and is approximately 1.55 mm thick. (a) How many quarters would have to be stacked to reach 575 ft, the height of the Washington Monument? (b) How much would this stack weigh? (c) How much money would this stack contain? (d) At the beginning of 2007, the national debt was $8.7 trillion. How many stacks like the one described would be necessary to pay off this debt?
1.67 The liquid substances mercury (density = 13.5 g/mL), water (1.00 g/mL), and cyclohexane (0.778 g/mL) do not form a solution when mixed, but separate in distinct layers. Sketch how the liquids would position themselves in a test tube.
1.73 A 40 lb container of peat moss measures 14 x 20 x 30 in. A 40 lb container of topsoil has a volume of 1.9 gal. (a) Calculate the average densities of peat moss and topsoil in units of g/cm3. Would it be correct to say that peat moss is "lighter" than topsoil? Explain. (b) How many bags of the peat moss are needed to cover an area measuring 10. ft by 20. ft to a depth of 2.0 in.?
1.81 In 2006, Professor Galen Suppes, from the University of Missouri-Columbia, was awarded a Presidential Green Challenge Award for his system of converting glycerin, C3H5(OH)3, a by-product of biodiesel production, to propylene glycol, C3H6(OH)2. Propylene glycol produced in this way will be cheap enough to replace the more toxic ethylene glycol that is the primary ingredient in automobile antifreeze. (a) If 50.0 mL of propylene glycol has a mass of 51.80 g, what is its density? (b) To obtain the same antifreeze protection requires 76 g of propylene glycol to replace each 62 g of ethylene glycol. Calculate the mass of propylene glycol required to replace 1.00 gal of ethylene glycol. The density of ethylene glycol is 1.12 g/mL. (c) Calculate the volume of propylene glycol, in gallons, needed to produce the same antifreeze protection as 1.00 gallon of ethylene glycol.
Farmasi, FKG, Fapet, FTIP, FPIK, Kimia, Biologi
1.11 Classify each of the following as a pure substance or a mixture. If a mixture, indicate whether it is homogeneous or heterogeneous: (a) rice pudding, (b) seawater.
1.19 Label each of the following as either a physical process or a chemical process: (b) melting of ice, (c) pulverizing an aspirin, (d) digesting a candy bar, (e) explosion of nitroglycerin.
1.21 Suggest a method of separating each of the following mixtures into two components: (a) sugar and sand.
1.47 (a) How many liters of wine can be held in a wine barrel whose capacity is 31 gal? (FTIP)
1.47 (b) The recommended adult dose of Elixophyllin®, a drug used to treat asthma, is 6 mg/kg of body mass. Calculate the dose in milligrams for a 150-lb person. (Farmasi, FKG, Kimia, Biologi)
1.47 (d) A pound of coffee beans yields 50 cups of coffee (4 cups = 1 qt). How many milliliters of coffee can be obtained from 1 g of coffee beans? (FTIP)
1.58 A sample of ascorbic acid (vitamin C) is synthesized in the laboratory. It contains 1.50 g of carbon and 2.00 g of oxygen. Another sample of ascorbic acid isolated from citrus fruits contains 6.35 g of carbon. How many grams of oxygen does it contain? Which law are you assuming in answering this question?
1.76 A 15.0-cm long cylindrical glass tube, sealed at one end, is filled with ethanol. The mass of ethanol needed to fill the tube is found to be 11.86 g. The density of ethanol is 0.789 g/mL. Calculate the inner diameter of the tube in centimeters.
1.79 Chromatography (Figure 1.14) is a simple, but reliable, method for separating a mixture into its constituent substances. Suppose you are using chromatography to separate a mixture of two substances. How would you know whether the separation is successful? Can you propose a means of quantifying how good or how poor the separation is?
1.1 (a) Pure element: i, v (b) mixture of elements: vi (c) pure compound: iv (d) mixture of an element and a compound: ii, iii
1.4 The aluminum sphere (density = 2.70 g/cm3) is lightest, then nickel (density = 8.90 g/cm3), then silver (density = 10.49 g/cm3).
1.6 (a) 7.5 cm, 2 significant figures (sig figs) (b) 140 C, 2 sig figs
1.8 (a) 2 significant figures (sig figs) (b) 2 sig figs
1.11 (a) Heterogeneous mixture (b) homogeneous mixture (heterogeneous if there are undissolved particles) (c) pure substance (d) homogeneous mixture.
1.13 (a) S (b) Mg (c) K (d) Cl (e) Cu (f) fluorine (g) nickel (h) sodium (i) aluminum G) silicon 1.15 C is a compound; it contains carbon and oxygen. A is a compound; it contains at
least carbon and oxygen. B is not defined by the data given; it is probably a compound because few elements exist as white solids.
1.17 Physical properties: silvery white; lustrous; melting point = 649 C; boiling point = 1105 C; density at 20 C = 1.738 g/cm3; pounded into sheets; drawn into wires; good conductor. Chemical properties: burns in air; reacts with Cl2.
1.19 (a) Chemical (b) physical (c) physical (d) chemical (e) chemical
1.21 (a) Add water to dissolve the sugar; filter this mixture, collecting the sand on filter paper and the sugar water in a flask. Evaporate water from the flask to recover solid sugar. (b) Heat the mixture until sulfur melts, then decant the liquid sulfur.
1.23 (a) 1 x 10-1 (b) 1 x 10-2 (c) 1 x 10-15 (d) 1 x 10-6 (e) 1 x 106 (f) 1 x 103 (g) 1 x 10-9
(h) 1 x 10-3 (i) 1 x 10-12
1.25 (a) 17 'C (b) 422.1 F (c) 506 K (d) 108 F (e) 1644 K
1.27 (a) 1.59 g/ mL. Carbon tetrachloride, 1.59 g/mL, is more dense than water, 1.00 g/mL; carbon tetrachloride will sink rather than float on water. (b) 1.609 kg (c) 50.35 cm3
1.29 (a) Calculated density = 0.86 g/mL. The substance is probably toluene, density = 0.866 g/mL. (b) 40.4 mL ethiene glycol (c) 1.11 x 103 g nickel
1.31 4.6 x 10-8 m; 46 nm
1.33 Exact: (c), (d), and (f)
1.35 (a) 3 (b) 2 (c) 5 (d) 3 (e) 5
1.37 (a) 1.025 x 102 (b) 6.570 x 105 (c) 8.543 x 10-3 (d) 2.579 x 10-4 (e) -3.572 x 10-2 1.39 (a) 21.11 (b) 237.4 (c) 652 (d) 7.66 x 10-2
1.41 (a) 1 X 106 nm/mm (b) 1 X 10-6 kg/mg (c) 3.28 X 103 km/ft (d) 16.4 cm3/in3
1.43 (a) 76 mL (b) 50. nm (c) 6.88 x 10-4 s (d) 2.3 x 102 g (e) 1.55 g/L (f) 6.151 x 10-3 L/s
1.45 (a) 4.32 x 105 s (b) 88.5 m (c) $0.499/L (d) 46.6 km/hr (e) 1.420 L/s (f) 707.9 cm3
1.47 (a) 1.2 x 102 L (b) 4 x 102 mg (c) 9.64 km/L (d) 26 mL
1.49 52 kg air
1.51 Use the cm as a unit for comparison (1 in. 2.5 cm). 57 cm = 57 cm; 14 in. 35 cm; 1.1 m = 110 cm. The order of length from shortest to longest is 14 in. < 57 cm < 1.1 m.
1.53 (a) $0.91 (b) Since coins come in integer numbers, 3 coins are required .
1.55 Composition is the contents of a substance; structure is the arrangement of these contents. 1.58 8.47 g O; the law of constant composition
1.61 (a) Volume (b) area (c) volume (d) density (e) time (f) length (g) temperature
1.64 (a) 1.13 x 105 quarters (b) 6.41 x 105 g (c) $2.83 x 104 (d) 3.1 x 108 stacks (approximately
310 million stacks!)
1.67 The most dense liquid, Hg, will sink; the least dense, cyclohexane, will float; H2O will be in the middle.
1.70 Density of solid = 1.63 g/mL
1.73 (a) Density of peat = 0.13 g/cm3, density of topsoil =
2.5 g/cm3. It is not correct to say that peat is "lighter" than
topsoil. Volumes must be specified in order to compare masses.
(b) Buy 7 bags of peat (6.9 are needed).
1.76 The inner diameter of the tube is 1.13 cm.
1.79 The separation is successful if two distinct spots are seen on the paper. To quantify the characteristics of the separation, calculate a reference value for each spot: distance travelled by spot/distance travelled by solvent. If the values for the two spots are fairly different,
the separation is successful.
1.81 (a) Density = 1.04 g/mL (b) 5.2 x 103 g propylene glycol provide the same antifreeze
protection as 1.00 gal of ethylene glycol. (c) 1.3 gal propylene glycol provide the same antifreeze protection as 1.00 gal of ethylene glycol.
Does the following diagram represent a chemical or physical change? How do you know? [Section 1.3]
The following dartboards illustrate the types of errors often seen when one measurement is repeated several times. The bull's-eye represents the "true value," and the darts represent the experimental measurements.
Which board best represents each of the following scenarios:
(a) measurements both accurate and precise,
(b) measurements precise but inaccurate,
(c) measurements imprecise but yield an accurate average?