Chapter 1

These questions are designed to be used by groups of students in class. Paracelsus, a sixteenth-century alchemist and healer, adopted as his slogan: "The patients are your textbook, the sickbed is your study." Is this view consistent with using the scientific method?

Which of the following is true about an individual atom? Explain. a. An individual atom should be considered to be a solid. b. An individual atom should be considered to be a liquid. c. An individual atom should be considered to be a gas. d. The state of the atom depends on which element it is. e. An individual atom cannot be considered to be a solid, liquid, or gas. Justify your choice, and for choices you did not pick, explain what is wrong with them.

These questions concern the work of J. J. Thomson. a. From Thomson's work, which particles do you think he would feel are most important for the formation of compounds (chemical changes), and why? b. Of the remaining two subatomic particles, which do you place second in importance for forming compounds, and why? c. Propose three models that explain Thomson's findings and evaluate them. To be complete you should include Thomson's findings.

Which of the following explain how an ion is formed? Explain your answer. a. adding or subtracting protons to/from an atom b. adding or subtracting neutrons to/from an atom c. adding or subtracting electrons to/from an atom

You may have noticed that when water boils, you can see bubbles that rise to the surface of the water. Which of the following is inside these bubbles? Explain. a. air b. hydrogen and oxygen gas c. oxygen gas d. water vapor e. carbon dioxide gas

One of the best indications of a useful theory is that it raises more questions for further experimentation than it originally answered. Does this apply to Dalton's atomic theory? Give examples.

Dalton assumed that all atoms of the same element were identical in all their properties. Explain why this assumption is not valid.

Which (if any) of the following can be determined by knowing the number of protons in a neutral element? Explain your answer. a. the number of neutrons in the neutral element b. the number of electrons in the neutral element c. the name of the element

A blue question or exercise number indicates that the answer to that question or exercise appears at the back of this book and a solution appèars in the Student Solutions Manual. The difference between a law and a theory is the difference between what and why. Explain.

Explain the fundamental steps of the scientific method. The scientific method is a dynamic process. What does this mean?

When hydrogen is burned in oxygen to form water, the composition of water formed does not depend on the amount of oxygen reacted. Interpret this in terms of the law of definite proportion.

Explain the law of conservation of mass, the law of definite proportion, and the law of multiple proportions.

Section I-5 describes the postulates of Dalton's atomic theory. With some modifications, these postulates hold up very well regarding how we view elements, compounds, and chemical reactions today. Answer the following questions concerning Dalton's atomic theory and the modifications made today. a. The atom can be broken down into smaller parts. What are the smaller parts? b. How are atoms of hydrogen identical to each other and how can they be different from each other? c. How are atoms of hydrogen different from atoms of helium? How can H atoms be similar to He atoms? d. How is water different from hydrogen peroxide \(\left(\mathrm{H}_{2} \mathrm{O}_{2}\right)\) even though both compounds are composed of only hydrogen and oxygen? e. What happens in a chemical reaction and why is mass conserved in a chemical reaction?

The contributions of J. J. Thomson and Ernest Rutherford led the way to today's understanding of the structure of the atom. What were their contributions?

What is the modern view of the structure of the atom?

The number of protons in an atom determines the identity of the atom. What do the number and arrangement of the electrons in an atom determine? What does the number of neutrons in an atom determine?

If the volume of a proton is similar to the volume of an electron, how will the densities of these two particles compare to each other?

For lighter, stable isotopes, the ratio of the mass number to the atomic number is close to a certain value. What is the value? What happens to the value of the mass number to atomic number ratio as stable isotopes become heavier?

When mixtures of gaseous \(\mathrm{H}_{2}\) and gaseous \(\mathrm{Cl}_{2}\) react, a product forms that has the same properties regardless of the relative amounts of \(\mathrm{H}_{2}\) and \(\mathrm{Cl}_{2}\) used. a. How is this result interpreted in terms of the law of definite proportion? b. When a volume of \(\mathrm{H}_{2}\) reacts with an equal volume of \(\mathrm{Cl}_{2}\) at the same temperature and pressure, what volume of product having the formula HCl is formed?

Observations of the reaction between nitrogen gas and hydrogen gas show us that 1 volume of nitrogen reacts with 3 volumes of hydrogen to make 2 volumes of gaseous product, as shown below: Determine the formula of the product and justify your answer.

A sample of chloroform is found to contain \(12.0 \mathrm{g}\) of carbon, \(106.4 \mathrm{g}\) of chlorine, and \(1.01 \mathrm{g}\) of hydrogen. If a second sample of chloroform is found to contain \(30.0 \mathrm{g}\) of carbon, what is the total mass of chloroform in the second sample?

A sample of \(\mathrm{H}_{2} \mathrm{SO}_{4}\) contains \(2.02 \mathrm{g}\) of hydrogen, \(32.07 \mathrm{g}\) of sulfur, and \(64.00 \mathrm{g}\) of oxygen. How many grams of sulfur and grams of oxygen are present in a second sample of \(\mathrm{H}_{2} \mathrm{SO}_{4}\) containing 7.27 g of hydrogen?

Hydrazine, ammonia, and hydrogen azide all contain only nitrogen and hydrogen. The mass of hydrogen that combines with \(1.00 \mathrm{g}\) of nitrogen for each compound is \(1.44 \times 10^{-1} \mathrm{g}\) \(2.16 \times 10^{-1} \mathrm{g},\) and \(2.40 \times 10^{-2} \mathrm{g},\) respectively. Show how these data illustrate the law of multiple proportions.

Consider 100.0 -g samples of two different compounds consisting only of carbon and oxygen. One compound contains \(27.2 \mathrm{g}\) of carbon and the other has \(42.9 \mathrm{g}\) of carbon. How can these data support the law of multiple proportions if 42.9 is not a multiple of \(27.2 ?\) Show that these data support the law of multiple proportions.

The three most stable oxides of carbon are carbon monoxide (CO), carbon dioxide \(\left(\mathrm{CO}_{2}\right),\) and carbon suboxide \(\left(\mathrm{C}_{3} \mathrm{O}_{2}\right) .\) The molecules can be represented as Explain how these molecules illustrate the law of multiple proportions.

Two elements, \(\mathrm{R}\) and \(\mathrm{Q}\), combine to form two binary compounds. In the first compound, \(14.0 \mathrm{g}\) of \(\mathrm{R}\) combines with \(3.00 \mathrm{g}\) of \(\mathbf{Q .}\) In the second compound, \(7.00 \mathrm{g}\) of \(\mathbf{R}\) combines with \(4.50 \mathrm{g}\) of \(\mathrm{Q}\). Show that these data are in accord with the law of multiple proportions. If the formula of the second compound is \(\mathrm{RQ}\), what is the formula of the first compound?

In Section 1-1 of the text, the concept of a chemical reaction was introduced with the example of the decomposition of water, represented as follows: Use ideas from Dalton's atomic theory to explain how the above representation illustrates the law of conservation of mass.

In a combustion reaction, \(46.0 \mathrm{g}\) of ethanol reacts with \(96.0 \mathrm{g}\) of oxygen to produce water and carbon dioxide. If \(54.0 \mathrm{g}\) of water is produced, what mass of carbon dioxide is produced?

Indium oxide contains \(4.784 \mathrm{g}\) of indium for every \(1.000 \mathrm{g}\) of oxygen. In \(1869,\) when Mendeleev first presented his version of the periodic table, he proposed the formula \(\operatorname{In}_{2} \mathrm{O}_{3}\) for indium oxide. Before that time it was thought that the formula was InO. What values for the atomic mass of indium are obtained using these two formulas? Assume that oxygen has an atomic mass of \(16.00 .\)

From the information in this chapter on the mass of the proton, the mass of the electron, and the sizes of the nucleus and the atom, calculate the densities of a hydrogen nucleus and a hydrogen atom.

In an experiment it was found that the total charge on an oil drop was \(5.93 \times 10^{-18} \mathrm{C}\). How many negative charges does the drop contain?

A chemist in a galaxy far, far away performed the Millikan oil drop experiment and got the following results for the charges on various drops. Use these data to calculate the charge of the electron in zirkombs. \(2.56 \times 10^{-12}\) zirkombs \(7.68 \times 10^{-12}\) zirkombs \(3.84 \times 10^{-12}\) zirkombs \(6.40 \times 10^{-13}\) zirkombs

Write the symbol of each atom using the \(_{z}^{\text {A }}\)X format.

For carbon-14 and carbon-12, how many protons and neutrons are in each nucleus? Assuming neutral atoms, how many electrons are present in an atom of carbon-14 and in an atom of carbon- \(12 ?\)

How many protons and neutrons are in the nucleus of each of the following atoms? In a neutral atom of each element, how many electrons are present? a. \(^{79} \mathrm{Br}\) d. \(^{133} \mathrm{Cs}\) b. \(^{81} \mathrm{Br}\) e. \(^{3} \mathrm{H}\) c. \(^{239} \mathrm{Pu}\) f. \(^{56} \mathrm{Fe}\)

What number of protons and neutrons is contained in the nucleus of each of the following atoms? Assuming each atom is uncharged, what number of electrons is present? a. \(\frac{235}{92} \mathrm{U}\) b. \(_{13}^{2} \mathrm{Al}\) c. \(\frac{57}{26} \mathrm{Fe}\) d. \(\frac{208}{82} \mathrm{Pb}\) e. \(\frac{86}{32} \mathrm{Rb}\) f. \(\frac{41}{20} \mathrm{Ca}\)

Write the atomic symbol \(\left(\frac{4}{2} X\right)\) for each of the following isotopes. a. \(Z=8,\) number of neutrons \(=9\) b. the isotope of chlorine in which \(A=37\) c. \(Z=27, A=60\) d. number of protons \(=26,\) number of neutrons \(=31\) e. the isotope of I with a mass number of 131 f. \(Z=3,\) number of neutrons \(=4\)

Write the atomic symbol \(\left(\frac{1}{2} X\right)\) for each of the isotopes described below. a. number of protons \(=27,\) number of neutrons \(=31\) b. the isotope of boron with mass number 10 c. \(Z=12, A=23\) d. atomic number \(53,\) number of neutrons \(=79\) e. \(Z=20,\) number of neutrons \(=27\) f. number of protons \(=29,\) mass number 65

For each of the following ions, indicate the number of protons and electrons the ion contains. a. \(\mathrm{Ba}^{2+}\) b. \(\mathrm{Zn}^{2+}\) c. \(\mathrm{N}^{3-}\) d. \(\mathrm{Rb}^{+}\) e. \(\mathrm{Co}^{3+}\) f. \(\mathrm{Te}^{2-}\) g. \(\mathrm{Br}^{-}\)

What is the symbol for an ion with 63 protons, 60 electrons, and 88 neutrons? If an ion contains 50 protons, 68 neutrons, and 48 electrons, what is its symbol?

What is the symbol of an ion with 16 protons, 18 neutrons, and 18 electrons? What is the symbol for an ion that has 16 protons, 16 neutrons, and 18 electrons?

Four \(\mathrm{Fe}^{2+}\) ions are key components of hemoglobin, the protein that transports oxygen in the blood. Assuming that these ions are \(^{53} \mathrm{Fe}^{2+}\), how many protons and neutrons are present in each nucleus, and how many electrons are present in each ion?

Which of the following statements is/are true? For the false statements, correct them. a. All particles in the nucleus of an atom are charged. b. The atom is best described as a uniform sphere of matter in which electrons are embedded. c. The mass of the nucleus is only a very small fraction of the mass of the entire atom. d. The volume of the nucleus is only a very small fraction of the total volume of the atom. e. The number of neutrons in a neutral atom must equal the number of electrons.

Identify each of the following elements. Give the number of protons and neutrons in each nucleus. a. \({ }_{15}^{31} \mathrm{X}\) b. \({ }_{53}^{127} \mathrm{X}\) c. \({ }_{19}^{39} \mathrm{X}\) d. \({ }_{70}^{173} \mathrm{X}\)

The isotope of an unknown element, \(\mathrm{X},\) has a mass number of 79\. The most stable ion of this isotope has 36 electrons and has a \(2-\) charge. Which of the following statements is(are) true? For the false statements, correct them. a. This ion has more electrons than protons in the nucleus. b. The isotope of \(X\) contains 38 protons. c. The isotope of \(X\) contains 41 neutrons. d. The identity of \(\mathrm{X}\) is strontium, \(\mathrm{Sr}\).

An element's most stable ion has a \(2+\) charge. If the ion of element \(\mathrm{X}\) has a mass number of 230 and has 86 electrons, what is the identity of the element, and how many neutrons does it have?

The early alchemists used to do an experiment in which water was boiled for several days in a sealed glass container. Eventually, some solid residue would appear in the bottom of the flask, which was interpreted to mean that some of the water in the flask had been converted into "earth." When Lavoisier repeated this experiment, he found that the water weighed the same before and after heating and the mass of the flask plus the solid residue equaled the original mass of the flask. Were the alchemists correct? Explain what happened. (This experiment is described in the article by A. F. Scott in Scientific American, January \(1984 .\)

In a reaction, \(34.0 \mathrm{g}\) of chromium(III) oxide reacts with \(12.1 \mathrm{g}\) of aluminum to produce chromium and aluminum oxide. If \(23.3 \mathrm{g}\) of chromium is produced, what mass of aluminum oxide is produced? )

Which of the following is(are) correct? a. \(^{40} \mathrm{Ca}^{2+}\) contains 20 protons and 18 electrons. b. Rutherford created the cathode-ray tube and was the founder of the charge- to-mass ratio of an electron. c. An electron is heavier than a proton. d. The nucleus contains protons, neutrons, and electrons.

Reaction of \(2.0 \mathrm{L}\) of hydrogen gas with \(1.0 \mathrm{L}\) of oxygen gas yields 2.0 L of water vapor. All gases are at the same temperature and pressure. Show how these data support the idea that oxygen gas is a diatomic molecule. Must we consider hydrogen to be a diatomic molecule to explain these results?