1.7 End oF Module 1 Questions

1. Define combustion and discuss the contributions made by Priestley and Lavoisier toward understanding a combustion reaction.

2.  Chemical engineers frequently use the concept of “mass balance” in their calculations, in which the mass of the reactants must equal the mass of the products. What law supports this practice?  Why does it support the concept of “mass balance.”

3.  Does the law of multiple proportions apply to both mass ratios and atomic ratios? Why or why not?

4.  What are the four hypotheses of the atomic theory of matter?

5.  One of the minerals found in soil has an Al:Si:O atomic ratio of 0.2:0.2:0.5. Is this consistent with the law of multiple proportions? Why or why not? Is the ratio of elements consistent with Dalton’s atomic theory of matter?

6.  Nitrogen and oxygen react to form three different compounds that contain 0.571 g, 1.143 g, and 2.285 g of oxygen/gram of nitrogen, respectively. Is this consistent with the law of multiple proportions? Explain your answer.

7.  Three binary compounds of vanadium and oxygen are known. The following table gives the masses of oxygen that combine with 10.00 g of vanadium to form each compound.

Determine the ratio of the masses of oxygen that combine with 3.14 g of vanadium in compounds A and B.  Predict the mass of oxygen that would combine with 3.14 g of vanadium to form the third compound in the series.

8.  Classify each statement as a law, a theory, an experiment, a hypothesis, a qualitative observation, or a quantitative observation.

a. Measured amounts of acid were added to a Rolaids tablet to see whether it really “consumes 47 times its weight in excess stomach acid.”

b. Heat always flows from hot objects to cooler ones, not in the opposite direction.

c. The universe was formed by a massive explosion that propelled matter into a vacuum.

d. Michael Jordan is the greatest pure shooter ever to play professional basketball.

e. Limestone is relatively insoluble in water but dissolves readily in dilute acid with the evolution of a gas.

f. Gas mixtures that contain more than 4% hydrogen in air are potentially explosive.

9. What are the three components of the scientific method?

10, Is it necessary for an individual to conduct experiments to follow the scientific method?

11. Identify each statement as a theory or a law and explain your reasoning.

a. The ratio of elements in a pure substance is constant.

b. An object appears black because it absorbs all the visible light that strikes it.

c. Energy is neither created nor destroyed.

d. Metals conduct electricity because their electrons are not tightly bound to a particular nucleus and are therefore free to migrate.

12. Identify each statement as a theory or a law and explain your reasoning.

a. A pure chemical substance contains the same proportion of elements by mass.

b. The universe is expanding.

c. Oppositely charged particles attract each other.

d. Life exists on other planets.

13. Classify each statement as a qualitative observation or a quantitative observation.

a. Mercury and bromine are the only elements that are liquids at room temperature.

b. An element is both malleable and ductile.

c. The density of iron is 7.87 g/cm3.

d. Lead absorbs sound very effectively.

14. Classify each statement as a quantitative observation or a qualitative observation.

a. Nickel deficiency in rats is associated with retarded growth.

b. Boron is a good conductor of electricity at high temperatures.

c. There are 1.4–2.3 g of zinc in an average 70 kg adult.

d. Certain osmium compounds found in air in concentrations as low as 10.7 µg/m3 can cause lung cancer.

15.  Given the volumes and masses of five samples of compounds used in blending gasoline, together with the densities of several chemically pure liquids, identify as many of the samples as possible.

16. What is the difference between mass and weight? Is the mass of an object on Earth the same as the mass of the same object on Jupiter? Why or why not?

17.  Is it accurate to say that a substance with a mass of 1 kg weighs 2.2 lb? Why or why not?

18.  Construct a table with the headings “Solid,” “Liquid,” and “Gas.” For any given substance, state what you expect for each of the following: the relative densities of the three phases, the physical shapes of the three phases, the volumes for the same mass of compound, the sensitivity of the volume of each phase to changes in temperature, the sensitivity of the volume to changes in pressure.

19. Classify each substance as homogeneous or heterogeneous and explain your reasoning: platinum, a carbonated beverage, bronze, wood, natural gas, Styrofoam

20. Classify each substance as homogeneous or heterogeneous and explain your reasoning: snowflakes, gasoline, black tea, plastic wrap, blood, water containing ice cubes

21. Classify each substance as a pure substance or a mixture and explain your reasoning: seawater, coffee, 14-karat gold, diamond, distilled water

22.  Classify each substance as a pure substance or a mixture: cardboard, caffeine, tin, a vitamin tablet, helium gas.

23.  Classify each substance as an element or a compound: sugar, silver, rust, rubbing alcohol, copper.

24. Classify each substance as an element or a compound: water, iron, hydrogen gas, glass, nylon

25. What techniques could be used to separate each of the following? Sugar and water from an aqueous solution of sugar, a mixture of sugar and sand, a heterogeneous mixture of solids with different solubilities.

26. What techniques could be used to separate each of the following? Solid calcium chloride from a solution of calcium chloride in water, the components of a solution of vinegar in water, particulates from water in a fish tank.

27. Classify each statement as an extensive property or an intensive property: carbon, in the form of diamond, is one of the hardest known materials. A sample of crystalline silicon, a grayish solid, has a mass of 14.3 g.  Germanium has a density of 5.32 g/cm3.  Gray tin converts to white tin at 13.2°C.  Lead is a bluish-white metal.

28. Classify each statement as a physical property or a chemical property: fluorine etches glass, chlorine interacts with moisture in the lungs to produce a respiratory irritant, bromine is a reddish-brown liquid.

29.  If a person weighs 176 lb on Earth, what is his or her mass on Mars, where the force of gravity is 37% of that on Earth?

30,  If a person weighs 135 lb on Earth, what is his or her mass on Jupiter, where the force of gravity is 236% of that on Earth?

31.  Calculate the volume of 10.00 g of each element and then arrange the elements in order of decreasing volume. The numbers in parentheses are densities.

copper (8.92 g/cm3)

calcium (1.54 g/cm3)

titanium (4.51 g/cm3)

iridium (22.85 g/cm3)

32. Given 15.00 g of each element, calculate the volume of each and then arrange the elements in order of increasing volume. The numbers in parentheses are densities.

gold (19.32 g/cm³)

lead (11.34 g/cm³)

iron (7.87 g/cm³)

sulfur (2.07 g/cm³)

33.  A silver bar has dimensions of 10.00 cm × 4.00 cm × 1.50 cm, and the density of silver is 10.49 g/cm³. What is the mass of the bar?

34.  Platinum has a density of 21.45 g/cm³. What is the mass of a platinum bar measuring 3.00 cm × 1.50 cm × 0.500 cm?

35.  Complete the following table.

36.  Gold has a density of 19.30 g/cm³. If a person who weighs 85.00 kg (1 kg = 1000 g) were given his or her weight in gold, what volume (in cm³) would the gold occupy? Are we justified in using the SI unit of mass for the person’s weight in this case?

An irregularly shaped piece of magnesium with a mass of 11.81 g was dropped into a graduated cylinder partially filled with water. The magnesium displaced 6.80 mL of water. What is the density of magnesium?

37.  The density of copper is 8.92 g/cm³. If a 10.00 g sample is placed in a graduated cylinder that contains 15.0 mL of water, what is the total volume that would be occupied?

At 20°C, the density of fresh water is 0.9982 kg/m3, and the density of seawater is 1.025 kg/m3. 38. Will a ship float higher in fresh water or in seawater? Explain your reasoning.

39.  Label each of the following changes as a physical or chemical change. Give evidence to support your answer.

1. Boiling water
2. A nail rusting
3. A green solution and colorless solution are mixed. The resulting mixture is a solution with a pale green color.
4. Two colorless solutions are mixed. The resulting mixture has a yellow precipitate.

40.  Convert each number to scientific notation.

a. 637.8

b. 0.0479

c. 7.86

d. 12,378

e. 0.00032

f. 61.06700

g. 2002.080

h. 0.01020

41.  Carry out the appropriate operation and then express the answer in scientific notation.

1. (1.36 × 10²) + (4.73 × 10³) (1.36 × 10²) + (4.73 × 10³)
2. (6.923 × 10⁻³) − (8.756 × 10⁻⁴) (6.923 × 10⁻³) − (8.756 × 10⁻⁴)

42.  Perform the appropriate operation and express your answer in scientific notation.

1. [(6.022 × 10²³) (6.42 × 10⁻²) [(6.022 × 10²³) (6.42 × 10⁻²)

43. Use the dimensional analysis (unit conversion, factor label) problem-solving method to answer the following questions.

a. How many nickels would you get for a twenty dollar bill?
b. How many hours are in a week?
c. How many revolutions does the hour hand on a clock make in a year?

44.  Find the number of centimeters in 1.00 x 10² yards.
45. Determine the number of meters in 1.00 mile.
46. The speed of light is 1.86 x 10⁵ miles per second. How many meters will light travel in 1.0 second?
47. Calculate the number of seconds in a year.
48. A light year is the distance that light travels in one year. Determine the number of miles, meters, and kilometers in one light year.
49. A single layer of gold atoms forms a surface whose dimensions are 1.0 x 10³ angstroms by 1.0 x 10³ angstroms. 1 angstrom = 10^–10 meter. a) What is the area of this surface in square angstroms?  b) What is the surface area in square centimeters?

50. The units of the chain system of measure, used by surveyors, are as follows:

• 7.92 inches = 1 link 
• 100 links = 1 chain
• 10 chains = 1 furlong 
• 80 chains = 1 mile

The distance of the Kentucky Derby, a classic horse race, is 1.25 miles. How is this distance expressed in furlongs?

51. A cube that has a length of 1 cm on each side has a volume of 1 cm³. How many cubic centimeters are in 1 cubic meter? (Hint: The answer is not 100.)