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Chemistry LibreTexts

1.E: Exercises

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  • Page ID
    41745
  • These are homework exercises to accompany Chapter 1 of the Ball et al. "The Basics of GOB Chemistry" Textmap.

    1.1: What Is Chemistry?

    Exercises

    1. Based on what you know, which fields are branches of science?

      1. meteorology (the study of weather)
      2. astrophysics (the physics of planets and stars)
      3. economics (the study of money and monetary systems)
      4. astrology (the prediction of human events based on planetary and star positions)
      5. political science (the study of politics)
    2. Based on what you know, which fields are a branches of science?

      1. history (the study of past events)
      2. ornithology (the study of birds)
      3. paleontology (the study of fossils)
      4. zoology (the study of animals)
      5. phrenology (using the shape of the head to determine personal characteristics)
    3. Which of the following are examples of matter?

      1. a baby
      2. an idea
      3. the Empire State Building
      4. an emotion
      5. the air
      6. Alpha Centauri, the closest known star (excluding the sun) to our solar system
    4. Which of the following are examples of matter?

      1. your textbook
      2. brain cells
      3. love
      4. a can of soda
      5. breakfast cereal
    5. Suggest a name for the science that studies the physics of rocks and the earth.

    6. Suggest a name for the study of the physics of living organisms.

    7. Engineering is the practical application of scientific principles and discoveries to develop things that make our lives easier. Is medicine science or engineering? Justify your answer.

    8. Based on the definition of engineering in Exercise 7, would building a bridge over a river or road be considered science or engineering? Justify your answer.

    9. When someone says, “I have a theory that excess salt causes high blood pressure,” does that person really have a theory? If it is not a theory, what is it?

    10. When a person says, “My hypothesis is that excess calcium in the diet causes kidney stones,” what does the person need to do to determine if the hypothesis is correct?

    11. Some people argue that many scientists accept many scientific principles on faith. Using what you know about the scientific method, how might you argue against that assertion?

    12. Most students take multiple English classes in school. Does the study of English use the scientific method?

    Answers

    1.  

      1. science
      2. science
      3. not science
      4. not science
      5. not science
     
    1.  

      1. matter
      2. not matter
      3. matter
      4. not matter
      5. matter
      6. matter
     
    1. geophysics

     
    1. Medicine is probably closer to a field of engineering than a field of science, but this may be arguable. Ask your doctor.

     
    1. In scientific terms, this person has a hypothesis.

     

    1. Science is based on reproducible facts, not blind belief.

    1.2: The Classification of Matter

    Exercises

    1. Does each statement refer to a chemical property or a physical property?

      1. Balsa is a very light wood.
      2. If held in a flame, magnesium metal burns in air.
      3. Mercury has a density of 13.6 g/mL.
      4. Human blood is red.
    2. Does each statement refer to a chemical property or a physical property?

      1. The elements sodium and chlorine can combine to make table salt.
      2. The metal tungsten does not melt until its temperature exceeds 3,000°C.
      3. The ingestion of ethyl alcohol can lead to disorientation and confusion.
      4. The boiling point of isopropyl alcohol, which is used to sterilize cuts and scrapes, is lower than the boiling point of water.
    3. Define element. How does it differ from a compound?

    4. Define compound. How does it differ from an element?

    5. Give two examples of a heterogeneous mixture.

    6. Give two examples of a homogeneous mixture.

    7. Identify each substance as an element, a compound, a heterogeneous mixture, or a solution.

      1. xenon, a substance that cannot be broken down into chemically simpler components
      2. blood, a substance composed of several types of cells suspended in a salty solution called plasma
      3. water, a substance composed of hydrogen and oxygen
    8. Identify each substance as an element, a compound, a heterogeneous mixture, or a solution.

      1. sugar, a substance composed of carbon, hydrogen, and oxygen
      2. hydrogen, the simplest chemical substance
      3. dirt, a combination of rocks and decaying plant matter
    9. Identify each substance as an element, a compound, a heterogeneous mixture, or a solution.

      1. air, primarily a mixture of nitrogen and oxygen
      2. ringer’s lactate, a standard fluid used in medicine that contains salt, potassium, and lactate compounds all dissolved in sterile water
      3. tartaric acid, a substance composed of carbon, hydrogen, and oxygen
    10. Identify each material as an element, a compound, a heterogeneous mixture, or a solution.

      1. equal portions of salt and sand placed in a beaker and shaken up
      2. a combination of beeswax dissolved in liquid hexane
      3. hydrogen peroxide, a substance composed of hydrogen and oxygen
    11. What word describes each phase change?

      1. solid to liquid
      2. liquid to gas
      3. solid to gas
    12. What word describes each phase change?

      1. liquid to solid
      2. gas to liquid
      3. gas to solid

    Answers

    1.  

      1. physical property
      2. chemical property
      3. physical property
      4. physical property
     
    1. An element is a substance that cannot be broken down into chemically simpler components. Compounds can be broken down into simpler substances.

     
    1. a salt and pepper mix and a bowl of cereal (answers will vary)

     
    1.  

      1. element
      2. heterogeneous mixture
      3. compound
     
    1.  

      1. solution
      2. solution
      3. compound
     
    1.  

      1. melting or fusion
      2. boiling or evaporation
      3. sublimation

    1.3: Measurements

    Exercises

    1. Why are both parts of a quantity important when describing it?

    2. Why are measurements an important part of any branch of science, such as chemistry?

    3. You ask a classmate how much homework your chemistry professor assigned. Your classmate answers, “twenty.” Is that a proper answer? Why or why not?

    4. Identify the number and the unit in each quantity.

      1. five grandchildren
      2. 16 candles
      3. four score and seven years
      4. 40 days and 40 nights
      5. 12.01 grams
      6. 9.8 meters per second squared
      7. 55 miles per hour
      8. 98.6 degrees Fahrenheit

    Answers

    1. The number states how much, and the unit states of what. Without the number and the unit, a quantity cannot be properly communicated.

     
    1. No, it is not a proper answer; you do not know whether the professor meant homework problem number 20 or 20 homework problems.

    1.4: Expressing Numbers: Scientific Notation

    Exercises

    1. Why is scientific notation useful in expressing numbers?

    2. What is the relationship between the power and the number of places a decimal point is moved when going from standard to scientific notation?

    3. Express each number in scientific notation.

      1. 0.00064
      2. 5,230,000
      3. −56,200
      4. 0.000000000220
      5. 1.0
    4. Express each number in scientific notation.

      1. 678
      2. −1,061
      3. 0.000560
      4. 0.0000003003
      5. 100,000,000
    5. Express each number in standard form.

      1. 6.72 × 104
      2. 2.088 × 10−4
      3. −3 × 106
      4. 9.98 × 10−7
    6. Express each number in standard form.

      1. 9.05 × 105
      2. 1.0 × 10−3
      3. 6.022 × 1023
      4. 8.834 × 10−12
    7. Complete the following table:

      Incorrect Scientific Notation Correct Scientific Notation
      54.7 × 104  
      0.0066 × 103  
      3,078 × 100  
    8. Complete the following table:

      Incorrect Scientific Notation Correct Scientific Notation
      234.0 × 101  
      36 × 10−4  
      0.993 × 105  

    Answers

    1. Scientific notation is more convenient than listing a large number of zeros.

     
    1.  

      1. 6.4 × 10−4
      2. 5.23 × 106
      3. −5.62 × 104
      4. 2.20 × 10−10
      5. 1.0 × 100
     
    1.  

      1. 67,200
      2. 0.0002088
      3. −3,000,000
      4. 0.000000998
     
    1. Incorrect Scientific Notation Correct Scientific Notation
      54.7 × 104 5.47 × 105
      0.0066 × 103 6.6 × 100
      3,078 × 100 3.078 × 103

    1.5: Expressing Numbers: Significant Figures

    Exercises

    1. Define significant figures. Why are they important?

    2. Define the different types of zeros found in a number and explain whether or not they are significant.

    3. How many significant figures are in each number?

      1. 140
      2. 0.009830
      3. 15,050
      4. 221,560,000
      5. 5.67 × 103
      6. 2.9600 × 10−5
    4. How many significant figures are in each number?

      1. 1.05
      2. 9,500
      3. 0.0004505
      4. 0.00045050
      5. 7.210 × 106
      6. 5.00 × 10−6
    5. Round each number to three significant figures.

      1. 34,705
      2. 34,750
      3. 34,570
    6. Round each number to four significant figures.

      1. 34,705
      2. 0.0054109
      3. 8.90443 × 108
    7. Perform each operation and express the answer to the correct number of significant figures.

      1. 467.88 + 23.0 + 1,306 = ?
      2. 10,075 + 5,822.09 − 34.0 = ?
      3. 0.00565 + 0.002333 + 0.0991 = ?
    8. Perform each operation and express the answer to the correct number of significant figures.

      1. 0.9812 + 1.660 + 8.6502 = ?
      2. 189 + 3,201.8 − 1,100 = ?
      3. 675.0 − 24 + 1,190 = ?
    9. Perform each operation and express the answer to the correct number of significant figures.

      1. 439 × 8,767 = ?
      2. 23.09 ÷ 13.009 = ?
      3. 1.009 × 876 = ?
    10. Perform each operation and express the answer to the correct number of significant figures.

      1. 3.00 ÷ 1.9979 = ?
      2. 2,300 × 185 = ?
      3. 16.00 × 4.0 = ?
    11. Use your calculator to solve each equation. Express each answer in proper scientific notation and with the proper number of significant figures. If you do not get the correct answers, you may not be entering scientific notation into your calculator properly, so ask your instructor for assistance.

      1. (5.6 × 103) × (9.04 × 10−7) = ?
      2. (8.331 × 10−2) × (2.45 × 105) = ?
      3. 983.09 ÷ (5.390 × 105) = ?
      4. 0.00432 ÷ (3.9001 × 103) = ?
    12. Use your calculator to solve each equation. Express each answer in proper scientific notation and with the proper number of significant figures. If you do not get the correct answers, you may not be entering scientific notation into your calculator properly, so ask your instructor for assistance.

      1. (5.2 × 106) × (3.33 × 10−2) = ?
      2. (7.108 × 103) × (9.994 × 10−5) = ?
      3. (6.022 × 107) ÷ (1.381 × 10−8) = ?
      4. (2.997 × 108) ÷ (1.58 × 1034) = ?

    Answers

    1. Significant figures represent all the known digits plus the first estimated digit of a measurement; they are the only values worth reporting in a measurement.

     
    1.  

      1. two
      2. four
      3. four
      4. five
      5. three
      6. five
     
    1.  

      1. 34,700
      2. 34,800
      3. 34,600
     
    1.  

      1. 1,797
      2. 15,863
      3. 0.1071
     
    1.  

      1. 3,850,000
      2. 1.775
      3. 884
     
    1.  

      1. 5.1 × 10−3
      2. 2.04 × 104
      3. 1.824 × 10−3
      4. 1.11 × 10−6

    1.6: The International System of Units

    1. List four base units.

    2. List four derived units.

    3. How many meters are in 1 km? How many centimeters are in 1 m?

    4. How many grams are in 1 Mg? How many microliters are in 1 L?

    5. Complete the following table:

      Unit Abbreviation
      centiliter  
        ms
        cm
        kL
      micrometer  
    6. Complete the following table:

      Unit Abbreviation
      microliter  
      kilosecond  
        dL
        ns
      millimeter  
    7. What are some appropriate units for density?

    8. A derived unit for velocity, which is the change of position with respect to time, is meters per second (m/s). Give three other derived units for velocity.

    Answers

    1. second, meter, kilogram, and kelvin (answers will vary)

     
    1. 1,000; 100

     
    1. Unit Abbreviation
      centiliter cL
      millisecond ms
      centimeter cm
      kiloliter kL
      micrometer µm
     
    1. grams per liter, grams per milliliter, and kilograms per liter (answers will vary)

    1.7: Converting Units

    Exercises

    1. Give the two conversion factors you can construct using each pair of units.

      1. meters and kilometers
      2. liters and microliters
      3. seconds and milliseconds
    2. Give the two conversion factors you can construct using each pair of units.

      1. grams and centigrams
      2. millimeters and meters
      3. liters and megaliters
    3. How many meters are in 56.2 km?

    4. How many seconds are in 209.7 ms?

    5. How many microliters are in 44.1 L?

    6. How many megagrams are in 90.532 g?

    7. Convert 109.6 kg into micrograms. Express your final answer in scientific notation.

    8. Convert 3.8 × 105 mm into kilometers. Express your final answer in scientific notation.

    9. Convert 3.009 × 10−5 ML into centiliters. Express your final answer in scientific notation.

    10. Convert 99.04 dm into micrometers. Express your final answer in scientific notation.

    11. The density of ethyl alcohol is 0.79 g/mL. What is the mass of 340 mL of ethyl alcohol?

    12. The density of a certain fraction of crude oil is 1.209 g/mL. What is the mass of 13,500 mL of this fraction?

    13. The density of ethyl alcohol is 0.79 g/mL. What is the volume of 340 g of ethyl alcohol?

    14. The density of a certain component of crude oil is 1.209 g/mL. What is the volume of 13,500 g of this component?

    15. Vitamin C tablets can come in 500 mg tablets. How many of these tablets are needed to obtain 10 g of vitamin C?

    16. A tablet of penicillin contains 250 mg of the antibacterial drug. A prescription contains 44 tablets. What is the total mass of penicillin in the prescription?

    Answers

    1.  

      1. \(\mathrm{\dfrac{1,000\:m}{1\:km}\,;\:\dfrac{1\:km}{1,000\:m}}\)
         
      2. \(\mathrm{\dfrac{1,000,000\:\mu L}{1\:L}\,;\:\dfrac{1\:L}{1,000,000\:\mu L}}\)
         
      3. \(\mathrm{\dfrac{1,000\:ms}{1\:s}\,;\:\dfrac{1\:s}{1,000\:ms}}\)
     
    1. 5.62 × 104 m

     
    1. 4.41 × 107 µL

     
    1. 1.096 × 1011 µg

     
    1. 3.009 × 103 cL

     
    1. 270 g

     
    1. 430 mL

     
    1. 20 tablets

    1.8: Chapter Summary

    1. A sample of urine has a density of 1.105 g/cm3. What is the mass of 0.255 L of this urine?

    2. The hardest bone in the body is tooth enamel, which has a density of 2.91 g/cm3. What is the volume, in liters, of 75.9 g of tooth enamel?

    3. Some brands of aspirin have 81 mg of aspirin in each tablet. If a person takes 8 tablets per day, how many grams of aspirin is that person consuming every day?

    4. The US government has a recommended daily intake (RDI) of 5 µg of vitamin D per day. (The name recommended daily allowance was changed to RDI in 1997.) If milk contains 1.2 µg per 8 oz glass, how many ounces of milk are needed to supply the RDI of vitamin D?

    5. The population of the United States, according to the 2000 census, was 281.4 million people.

      1. How many significant figures does this number have?
      2. What is the unit in this quantity?
      3. Express this quantity in proper scientific notation.
    6. The United States produces 34,800,000,000 lb of sugar each year, and much of it is exported to other countries.

      1. How many significant figures does this number have?
      2. What is the unit in this quantity?
      3. Express this quantity in proper scientific notation.
    7. Construct a conversion factor that can convert from one unit to the other in each pair of units.

      1. from millimeters to kilometers
      2. from kilograms to micrograms
      3. from centimeters to micrometers
    8. Construct a conversion factor that can convert from one unit to the other in each pair of units.

      1. from kilometers to micrometers
      2. from decaliters to milliliters
      3. from megagrams to milligrams
    9. What is the density of a dextrose solution if 355 mL of the solution has a mass of 406.9 g?

    10. What is the density of a dental amalgam (an alloy used to fill cavities) if 1.005 kg of the material has a volume of 433 mL? Express your final answer in grams per milliliter.

    For Exercises 11–16, see the accompanying table for the relationships between English and SI units.

    1 m ≈ 39.36 in. ≈ 3.28 ft ≈ 1.09 yd
    1 cm ≈ 2.54 in.
    1 km ≈ 0.62 mi
    1 kg ≈ 2.20 lb
    1 lb ≈ 454 g
    1 L ≈ 1.06 qt
    1 qt ≈ 0.946 L
    1. Approximately how many inches are in 4.76 m?

    2. Approximately how many liters are in 1 gal, which is exactly 4 qt?

    3. Approximately how many kilograms are in a person who weighs 170 lb?

    4. The average distance between Earth and the sun is 9.3 × 107 mi. How many kilometers is that?

    5. Show mathematically that 1 L equals 1 dm3.

    6. Show mathematically that 1 L equals 1,000 cm3.

    Answers

    1. 282 g

     
    1. 650 mg

     
    1.  

      1. four significant figures
      2. people
      3. 2.841 × 108 people
     
    1.  

      1. \(\mathrm{\dfrac{1\:km}{10^6\:mm}}\)
         
      2. \(\mathrm{\dfrac{10^9\:\mu g}{1\:kg}}\)
         
      3. \(\mathrm{\dfrac{10^4\:\mu m}{1\:cm}}\)
     
    1. 1.15 g/mL

     
    1. 187 in.

     
    1. 77 kg

     
    1. \(\mathrm{1\:L=0.001\:m^3\times\left(\dfrac{1\:dm}{0.1\:m}\right)^3=1\:dm^3}\)