Classify each of the following as a pure substance or a mixture. lf a mixture, indicate

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]

Does the following diagram represent a chemical or physical change? How do you know? [Section 1.3]

Identify each of the following as measurements of length, area, volume, mass, density, time, or temperature: (a) 5 ns, (b) 5.5 kgjm3, (c) 0.88 pm, (d) 540 km2, (e) 173 K, (f) 2 mm3, (g) 23 oc. [Section 1.4]

Three spheres of equal size are composed of aluminum (density = 2.70 gjcm3), silver (density = 10.49 gjcm3), and nickel (density = 8.90 gjcm3). List the spheres from lightest to heaviest.

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? [Section 1.5]

(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]

What is wrong with the following statement? Twenty years ago an ancient artifact was determined to be 1900 years old. It must now be 1920 years old. [Section 1.5]

(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]

When you convert units, how do you decide which part of the conversion factor is in the numerator and which is in the denominator? [Section 1.6]

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, (c) magnesium, (d) gasoline.

Classify each of the following as a pure substance or a mixture. lf a mixture, indicate whether it is homogeneous or heterogeneous: (a) air, (b) tomato juice, (c) iodine crystals, (d) sand.

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) AI, (j) Si

Give the chemical symbol or name for each of the following elements, as appropriate: (a) carbon, (b) nitrogen, (c) bromine, (d) zinc, (e) iron, (f) P, (g) Ca, (h) He, (i) Pb, (j)Ag

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.

ln 1807 the English chemist Humphry Davy passed an electric current through molten potassium hydroxide and isolated a bright, shiny reactive substance. He claimed the discovery of a new element, which he named potassium. In those days, before the advent of modem instruments, what was the basis on which one could claim that a substance was an element?

1n 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 649 oc and boils at 1105 oc. Its density at 20 oc is 1.738 gjcm3 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?

Read the following description of the element zinc, and indicate which are physical properties and which are chemical properties. Zinc is a silver-gray-colored metal that melts at 420 oc. When zinc granules are added to dilute sulfuric acid, hydrogen is given off and the metal dissolves. Zinc has a hardness on the Mohs scale of 2.5 and a density of 7.13 g/cm3 at 25 oc. It reacts slowly with oxygen gas at elevated temperatures to form zinc oxide, ZnO.

Label each of the following as either a physical process or a chemical process: (a) corrosion of aluminum metal, (b) melting of ice, (c) pulverizing an aspirin, (d) digesting a candy bar, (e) explosion of nitroglycerin.

Suggest a method of separating each of the following mixtures into two components: (a) sugar and sand, (b) iron and sulfur

A beaker contains a clear, colorless liquid. If it is water, how could you determine whether it contained dissolved table salt? Do not taste it!

What exponential notation do the following abbreviations represent: (a) d, (b) c, (c) f, (d) J.l., (e) M, (f) k, (g) n, (h) m, (i) p?

Use appropriate metric prefixes to write the following measurements without use of exponents: (a) 6.35 X 10-2 L, (b) 6.5 X 10--<; s, (c) 9.5 X 10-4 m, (d) 4.23 X 10-9 m3, (e) 12.5 X 10-S kg, (f) 3.5 X 10-lO g, (g) 6.54 x 109 fs.

Make the following conversions: (a) 62 'F to 'C, (b) 216.7 'C to 'F, (c) 233 'C to K, (d) 315 K to 'F, (e) 2500 'F to K.

(a) The temperature on a warm summer day is 87 'F. What is the temperature in 'C? (b) Many scientific data are reported at 25 'C. What is this temperature in kelvins and in degrees Fahrenheit? (c) Suppose that a recipe calls for an oven temperature of 175 'F. Convert this temperature to degrees Celsius and to kelvins. (d) The melting point of sodium bromide (a salt) is 755 'C. Calculate this temperature in 'F and in kelvins. (e) Neon, a gaseous element at room temperature, is used to make electronic signs. Neon has a melting point of -248.6 'C and a boiling point of -246.1 'C. Convert these temperatures to kelvins.

(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?

(a) A cube of osmium metal 1.500 em on a side has a mass of 76.31 g at 25 'C. What is its density in g/cm3 at this temperature? (b) The density of titanium metal is 4.51 g/cm3 at 25 'C. What mass of titanium displaces 125.0 mL of water at 25 'C? (c) The density of benzene at 15 'C is 0.8787 gjmL. Calculate the mass of 0.1500 L of benzene at this temperature.

(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 gjmL) 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 gjmL. 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 em on each edge. If the metal is nickel, whose density is 8.90 g/cm3, what is the mass of the cube?

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?

A cylindrical rod formed from silicon is 16.8 em long and has a mass of 2.17 kg. The density of silicon is 2.33 g/cm3. What is the diameter of the cylinder? (The volume of a cylinder is given by 1Tr2h, where r is the radius, and h is its length.)

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.

Indicate which of the following are exact numbers: (a) the mass of a 32-oz can of coffee, (b) the number of students in your chemistry class, (c) the temperature of the surface of the sun, (d) the mass of a postage stamp, (e) the number of milliliters in a cubic meter of water, (f) the average height of students in your school.

What is the number of significant figures in each of the following measured quantities? (a) 358 kg, (b) 0.054 s, (c) 6.3050 em, (d) O.D105 L, (e) 7.0500 x w-3 m3.

Indicate the number of significant figures in each of the following measured quantities: (a) 3.774 km, (b) 205 m2, (c) 1.700 em, (d) 350.00 K, (e) 307.080 g.

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.

(a) The diameter of Earth at the equator is 7926.381 mi. Round this number to three significant figures, and express it in standard exponential notation. (b) The circumference of Earth through the poles is 40,008 km. Round this number to four significant figures, and express it in standard exponential notation.

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) (0.1050) (d) 0.0577/0.753

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) mrn to nm, (b) mg to kg, (c) krn to ft, (d) in 3 to cm3

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) I'm to mrn, (b) ms tons, (c) mi to km, (d) ftl to L.

Perform the following conversions: (a) 0.076 L to mL, (b) 5.0 x w-8 m to nm, (c) 6.88 x 105 ns to s, (d) 0.50 lb to g, (e) 1.55 kgjm3 to g/L, (f) 5.850 galjhr to Ljs.

(a) The speed of light in a vacuum is 2.998 X 108 m/s. Calculate its speed in km/hr. (b) The Sears Tower in Chicago is 1454 ft tall. Calculate its height in meters. (c) The Vehicle Assembly Building at the Kennedy Space Center in Florida has a volume of 3,666,500 m3 Convert this volume to liters, and express the result in standard exponential notation. (d) An individual suffering from a high cholesterol level in her blood has 232 mg of cholesterol per 100 mL of blood. If the total blood volume of the individual is 5.2 L, how many grams of total blood cholesterol does the individual's body contain?

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 krn/hr, (e) 22.50 gal/min to L/s, (f) 0.02500 ft3 to cm3

Carry out the following conversions: (a) 0.105 in. to mm, (b) 0.650 qt to mL, (c) 8.75 1-'m/s to km/hr, (d) 1.955 m3 to yd3, (e) $3.99/lb to dollars per kg, (f) 8.75 lb/ft3 to g/mL.

(a) How many liters of wine can be held in a wine barrel whose capacity is 31 gal? (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. (c) If an automobile is able to travel 254 mi on 11.2 gal of gasoline, what is the gas mileage in km/L? (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?

(a) If an electric car is capable of going 225 km on a single charge, how many charges will it need to travel from Boston, Massachusetts, to Miami, Florida, a distance of 1486 mi, assuming that the trip begins with a full charge? (b) lf a migrating loon flies at an average speed of 14 m/s, what is its average speed in mi/hr? (c) What is the engine piston displacement in liters of an engine whose displacement is listed as 450 in.3? (d) In March 1989 the Exxon Valdez ran aground and spilled 240,000 barrels of crude petroleum off the coast of Alaska. One barrel of petroleum is equal to 42 gal. How many liters of petroleum were spilled?

The density of air at ordinary atmospheric pressure and 25 oc 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?

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.

By using estimation techniques, determine which of the following is the heaviest and which is the lightest: a 5-lb bag of potatoes, a 5-kg bag of sugar, or 1 gal of water (density = 1.0 g/mL).

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?

A copper refinery produces a copper ingot weighing 150 lb. If the copper is drawn into wire whose diameter is 8.25 mm, how many feet of copper can be obtained from the ingot? The density of copper is 8.94 g/cm3 (Assume that the wire is a cylinder whose volume is V = 1rr2h, where r is its radius and h is its height or length.)

What is meant by the terms composition and structure when referring to matter?

(a) Classify each of the following as a pure substance, a solution, or a heterogeneous mixture: a gold coin, a cup of coffee, a wood plank. (b) What ambiguities are there in answering part (a) from the descriptions given?

(a) What is the difference between a hypothesis and a theory? (b) Explain the difference between a theory and a scientific law. Which addresses how matter behaves, and which addresses why it behaves that way?

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?

Two students determine the percentage of lead in a sample as a laboratory exercise. The true percentage is 22.52%. The students' results for three determinations are as follows: 1. 22.52, 22.48, 22.54 2. 22.64, 22.58, 22.62 (a) Calculate the average percentage for each set of data, and tell which set is the more accurate based on the average. (b) Precision can be judged by examining the average of the deviations from the average value for that data set. (Calculate the average value for each data set, then calculate the average value of the absolute deviations of each measurement from the average.) Which set is more precise?

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?

Give the derived SI units for each of the following quantities in base SI units: (a) acceleration = distancejtime2; (b) force = mass X acceleration; (c) work = force X distance; (d) pressure = force/ area; (e) power work/time.

The distance from Earth to the Moon is approximately 240,000 mi. (a) What is this distance in meters? (b) The peregrine falcon has been measured as traveling up to 350 km/hr in a dive. If this falcon could fly to the Moon at this speed, how many seconds would it take?

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?

In the United States, water used for irrigation is measured in acre-feet. An acre-foot of water covers an acre to a depth of exactly 1 ft. An acre is 4840 yd2 An acrefoot is enough water to supply two typical households for 1.00 yr. (a) If desalinated water costs $1950 per acrefoot, how much does desalinated water cost per liter? (b) How much would it cost one household per day if it were the only source of water?

Suppose you decide to define your own temperature scale using the freezing point ( -11.5 oC) and boiling point (197.6 oq of ethylene glycol. If you set the freezing point as 0 oG and the boiling point as 100 G, what is the freezing point of water on this new scale?

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.

Small spheres of equal mass are made of lead (density = 11.3 g/cm3 ), silver (10.5 g/cm3 ), and aluminum (2.70 gjcm3 ). Without doing a calculation, list the spheres in order from the smallest to the largest.

Water has a density of 0.997 gjcm3 at 25 oc; ice has a density of 0.917 g/cm3 at -10 oe, (a) If a soft-drink bottle whose volume is 1.50 L is completely filled with water and then frozen to -10 oc, what volume does the ice occupy? (b) Can the ice be contained within the bottle?

(a) You are given a bottle that contains 4.59 cm3 of a metallic solid. The total mass of the bottle and solid is 35.66 g. The empty bottle weighs 14.23 g. What is the density of the solid? (b) Mercury is traded by the "flask," a unit that has a mass of 34.5 kg. What is the volume of a flask of mercury if the density of mercury is 13.5 g/mL? (c) A thief plans to steal a gold sphere with a radius of 28.9 em from a museum. If the gold has a density of 19.3 g/cm3 what is the mass of the sphere? [The volume of a sphere is V = (4/3)m3 .] Is he likely to be able to walk off with it unassisted?

Automobile batteries contain sulfuric acid, which is commonly referred to as "battery acid." Calculate the number of grams of sulfuric acid in 0.500 L of battery acid if the solution has a density of 1.28 g/mL and is 38.1% sulfuric acid by mass.

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 gjcm3 . 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.?

A coin dealer offers to sell you an ancient gold coin that is 2.2 em in diameter and 3.0 mm in thickness. (a) The density of gold is 19.3 g/cm3 How much should the coin weigh if it is pure gold? (b) If gold sells for $640 per troy ounce, how much is the gold content worth? (1 troy ounce = 31.1 g).

A package of aluminum foil contains 50 ftl of foil, which weighs approximately 8.0 oz. Aluminum has a density of 2.70 g/cm3 What is the approximate thickness of the foil in millimeters?

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.

Gold is alloyed (mixed) with other metals to increase its hardness in making jewelry. (a) Consider a piece of gold jewelry that weighs 9.85 g and has a volume of 0.675 cm3 The jewelry contains onlj gold and silver, which have densities of 19.3 gjcm and 10.5 gjcm3, respectively. If the total volume of the jewelry is the sum of the volumes of the gold and silver that it contains, calculate the percentage of gold (by mass) in the jewelry. (b) The relative amount of gold in an alloy is commonly expressed in units of karats. Pure gold is 24-karat, and the percentage of gold in an alloy is given as a percentage of this value. For example, an alloy that is 50% gold is 12-karat. State the purity of the gold jewelry in karats.

Suppose you are given a sample of a homogeneous liquid. What would you do to determine whether it is a solution or a pure substance?

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?

In 2006, Professor Galen Suppes, from the University of Missouri-Columbia, was awarded a Presidential Green Challenge Award for his system of converting glycerin, C 3 H5(0H)3 , a by-product of biodiesel production, to propylene glycol, C3H6(0Hh. Propylene glycol proAdditional Exercises 35 duced 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.

The concepts of accuracy and precision are not always easy to grasp. Here are two sets of studies: (a) The mass of a secondary weight standard is determined by weighing it on a very precise balance under carefully controlled laboratory conditions. The average of 18 different weight measurements is taken as the weight of the standard. (b) A group of 10,000 males between the ages of 50 and 55 is surveyed to ascertain a relationship between calorie intake and blood cholesterol level. The survey questionnaire is quite detailed, asking the respondents about what they eat, smoking and drinking habits, and so on. The results are reported as showing that for men of comparable lifestyles, there is a 40% chance of the blood cholesterol level being above 230 for those who consume more than 40 calories per gram of body weight per day, as compared with those who consume fewer than 30 calories per gram of body weight per day. Discuss and compare these two studies in terms of the precision and accuracy of the result in each case. How do the two studies differ in nature in ways that affect the accuracy and precision of the results? What makes for high precision and accuracy in any given study? In each of these studies, what factors might not be controlled that could affect the accuracy and precision? What steps can be taken generally to attain higher precision and accuracy?