Chapter 2

Name each of the following binary, nonionic compounds: (a) \(\mathrm{NF}_{3}\) (b) HI (c) \(\mathrm{BI}_{3}\) (d) \(\mathrm{PF}_{5}\)

Name each of the following binary, nonionic compounds: (a) \(\mathrm{N}_{2} \mathrm{O}_{5}\) (b) \(\mathrm{P}_{4} \mathrm{S}_{3}\) (c) \(\mathrm{OF}_{2}\) (d) \(\mathrm{XeF}_{4}\)

Give the formula for each of the following compounds: (a) sulfur dichloride (b) dinitrogen pentaoxide (c) silicon tetrachloride (d) diboron trioxide (commonly called boric oxide

Give the formula for each of the following compounds: (a) bromine trifluoride (b) xenon difluoride (c) hydrazine (d) diphosphorus tetrafluoride (e) butane

Calculate the mass, in grams, of each the following: (a) 2.5 mol of aluminum (b) \(1.25 \times 10^{-3}\) mol of iron (c) 0.015 mol of calcium (d) 653 mol of neon

Calculate the amount (moles) represented by each of the following: (a) \(16.0 \mathrm{g}\) of \(\mathrm{Na}\) (b) \(0.876 \mathrm{g}\) of tin (c) \(0.0034 \mathrm{g}\) of platinum (d) 0.983 g of \(\mathrm{Xe}\)

You are given 1.0 -g samples of He, \(\mathrm{Fe}, \mathrm{Li}, \mathrm{Si}\), and C. Which sample contains the largest number of atoms? Which contains the smallest?

You are given 0.10-g samples of \(\mathrm{K}, \mathrm{Mo}, \mathrm{Cr},\) and \(\mathrm{Al}\). List the samples in order of the amount (moles), from smallest to largest.

Analysis of a 10.0-g sample of apatite (a major component of tooth enamel) showed that it was made up of \(3.99 \mathrm{g} \mathrm{Ca}, 1.85 \mathrm{g} \mathrm{P}, 4.14 \mathrm{g} \mathrm{O},\) and \(0.020 \mathrm{g}\) H. List these elements based on relative amounts (moles), from smallest to largest.

A semiconducting material is composed of \(52 \mathrm{g}\) of Ga, \(9.5 \mathrm{g}\) of \(\mathrm{Al}\), and \(112 \mathrm{g}\) of As. Which element has the largest number of atoms in this material?

Calculate the molar mass of each of the following compounds: (a) \(\mathrm{Fe}_{2} \mathrm{O}_{3},\) iron(III) oxide (b) \(\mathrm{BCl}_{3},\) boron trichloride (c) \(\left.\mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{6}, \text { ascorbic acid (vitamin } \mathrm{C}\right)\)

Calculate the molar mass of each of the following compounds: (a) \(\operatorname{Fe}\left(\mathrm{C}_{6} \mathrm{H}_{11} \mathrm{O}_{7}\right)_{2},\) iron(II) gluconate, a dietary supplement (b) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{SH},\) butanethiol, has a skunk-like odor (c) \(\mathrm{C}_{20} \mathrm{H}_{24} \mathrm{N}_{2} \mathrm{O}_{2},\) quinine, used as an antimalarial drug

Calculate the molar mass of each hydrated compound. Note that the water of hydration is included in the molar mass. (See page \(85 .\) ) (a) \(\mathrm{Ni}\left(\mathrm{NO}_{3}\right)_{2} \cdot 6 \mathrm{H}_{2} \mathrm{O}\) (b) \(\mathrm{CuSO}_{4} \cdot 5 \mathrm{H}_{2} \mathrm{O}\)

What mass is represented by 0.0255 mol of each of the following compounds? (a) \(\mathrm{C}_{3} \mathrm{H}_{7} \mathrm{OH}, 2\) -propanol, rubbing alcohol (b) \(\mathrm{C}_{11} \mathrm{H}_{16} \mathrm{O}_{2},\) an antioxidant in foods, also known as BHA (butylated hydroxyanisole) (c) \(\mathrm{C}_{9} \mathrm{H}_{8} \mathrm{O}_{4},\) aspirin (d) \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CO},\) acetone, an important industrial solvent

Sulfur trioxide, \(\mathrm{SO}_{3}\), is made industrially in enormous quantities by combining oxygen and sulfur dioxide, \(\mathrm{SO}_{2}\). What amount (moles) of \(\mathrm{SO}_{3}\) is represented by \(1.00 \mathrm{kg}\) of sulfur trioxide? How many molecules? How many sulfur atoms? How many oxygen atoms?

How many ammonium ions and how many sulfate ions are present in a 0.20 mol sample of \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4} ?\) How many atoms of \(\mathrm{N}, \mathrm{H}, \mathrm{S}\) and \(\mathrm{O}\) are contained in this sample?

Acetaminophen, whose structure is drawn below, is the active ingredient in some nonprescription pain killers. The recommended dose for an adult is two \(500-\mathrm{mg}\) caplets. How many molecules make up one dose of this drug?

An Alka-Seltzer tablet contains 324 mg of aspirin \(\left(\mathrm{C}_{9} \mathrm{H}_{8} \mathrm{O}_{4}\right), 1904 \mathrm{mg}\) of \(\mathrm{NaHCO}_{3},\) and \(1000 . \mathrm{mg}\) of citric acid \(\left(\mathrm{H}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7}\right) .\) (The last two compounds react with each other to provide the "fizz," bubbles of \(\mathrm{CO}_{2},\) when the tablet is put into water.) (a) Calculate the amount (moles) of each substance in the tablet. (b) If you take one tablet, how many molecules of aspirin are you consuming?

Calculate the mass percent of each element in the following compounds: (a) \(\mathrm{PbS}\), lead(II) sulfide, galena (b) \(\mathrm{C}_{3} \mathrm{H}_{8},\) propane (c) \(\mathrm{C}_{10} \mathrm{H}_{14} \mathrm{O},\) carvone, found in caraway seed oil

Calculate the mass percent of each element in the following compounds: (a) \(\mathrm{C}_{8} \mathrm{H}_{10} \mathrm{N}_{2} \mathrm{O}_{2},\) caffeine (b) \(\mathrm{C}_{10} \mathrm{H}_{20} \mathrm{O},\) menthol (c) \(\mathrm{CoCl}_{2} \cdot 6 \mathrm{H}_{2} \mathrm{O}\)

Calculate the mass percent of copper in CuS, copper(II) sulfide. If you wish to obtain \(10.0 \mathrm{g}\) of copper metal from copper(II) sulfide, what mass of CuS (in grams) must you use?

Calculate the mass percent of titanium in the mineral ilmenite, \(\mathrm{FeTiO}_{3} .\) What mass of ilmenite (in grams) is required if you wish to obtain \(750 \mathrm{g}\) of titanium?

Succinic acid occurs in fungi and lichens. Its empirical formula is \(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\), and its molar mass is \(118.1 \mathrm{g} / \mathrm{mol} .\) What is its molecular formula?

An organic compound has the empirical formula \(\mathrm{C}_{2} \mathrm{H}_{4} \mathrm{NO} .\) If its molar mass is \(116.1 \mathrm{g} / \mathrm{mol},\) what is the molecular formula of the compound?

Acetylene is a colorless gas used as a fuel in welding torches, among other things. It is \(92.26 \%\) C and \(7.74 \%\) H. Its molar mass is \(26.02 \mathrm{g} / \mathrm{mol}\). What are the empirical and molecular formulas of acetylene?

A large family of boron-hydrogen compounds has the general formula \(\mathrm{B}_{x} \mathrm{H}_{y}\). One member of this family contains \(88.5 \%\) B; the remainder is hydrogen. What is its empirical formula?

Cumene, a hydrocarbon, is a compound composed only of \(\mathrm{C}\) and \(\mathrm{H}\). It is \(89.94 \%\) carbon, and its molar mass is \(120.2 \mathrm{g} / \mathrm{mol}\). What are the empirical and molecular formulas of cumene?

In \(2006,\) a Russian team discovered an interesting molecule they called "sulflower" because of its shape and because it was based on sulfur. It is composed of \(57.17 \%\) S and \(42.83 \%\) C and has a molar mass of \(448.70 \mathrm{g} / \mathrm{mol} .\) Determine the empirical and molecular formulas of "sulflower."

Mandelic acid is an organic acid composed of carbon \((63.15 \%),\) hydrogen \((5.30 \%),\) and oxygen (31.55\%). Its molar mass is \(152.14 \mathrm{g} / \mathrm{mol.}\) Determine the empirical and molecular formulas of the acid.

Nicotine, a poisonous compound found in tobacco leaves, is \(74.0 \%\) C, \(8.65 \%\) H, and \(17.35 \%\) N. Its molar mass is \(162 \mathrm{g} / \mathrm{mol}\). What are the empirical and molecular formulas of nicotine?

A compound containing xenon and fluorine was prepared by shining sunlight on a mixture of Xe \((0.526 \mathrm{g})\) and excess \(\mathrm{F}_{2}\) gas. If you isolate \(0.678 \mathrm{g}\) of the new compound, what is its empirical formula?

Elemental sulfur (1.256 g) is combined with fluorine, \(\mathrm{F}_{2}\), to give a compound with the formula \(\mathrm{SF}_{x},\) a very stable, colorless gas. If you have isolated \(5.722 \mathrm{g}\) of \(\mathrm{SF}_{x},\) what is the value of \(x ?\)

Epsom salt is used in tanning leather and in medicine. It is hydrated magnesium sulfate, \(\mathrm{MgSO}_{4} \cdot 7 \mathrm{H}_{2} \mathrm{O} .\) The water of hydration is lost on heating, with the number lost depending on the temperature. Suppose you heat a \(1.394-\mathrm{g}\) sample at \(100^{\circ} \mathrm{C}\) and obtain \(0.885 \mathrm{g}\) of a partially hydrated sample, \(\mathrm{MgSO}_{4} \cdot x \mathrm{H}_{2} \mathrm{O} .\) What is the value of \(x ?\)

You combine \(1.25 \mathrm{g}\) of germanium, Ge, with excess chlorine, \(\mathrm{Cl}_{2}\). The mass of product, \(\mathrm{Ge}_{x} \mathrm{Cl}_{y}\) is 3.69 g. What is the formula of the product, \(\mathrm{Ge}_{x} \mathrm{Cl}_{y} ?\)

The highest mass peaks in the mass spectrum of \(\mathrm{Br}_{2}\) occur at \(m / Z 158,160,\) and \(162 .\) The ratio of intensities of these peaks is approximately \(1: 2: 1 .\) Bromine has two stable isotopes, \(^{79} \mathrm{Br}(50.7 \%\) abundance) and \(^{81} \mathrm{Br}(49.3 \%\) abundance). (a) What molecular species gives rise to each of these peaks? (b) Explain the relative intensities of these peaks. (Hint: Consider the probabilities of each atom combination.

Potassium has three naturally occurring isotopes \(\left(^{39} \mathrm{K},^{40} \mathrm{K}, \text { and }^{41} \mathrm{K}\right),\) but \(^{40} \mathrm{K}\) has a very low natural abundance. Which of the other two isotopes is more abundant? Briefly explain your answer.

Crossword Puzzle: In the \(2 \times 2\) box shown here, each answer must be correct four ways: horizontally, vertically, diagonally, and by itself. Instead of words, use symbols of elements. When the puzzle is complete, the four spaces will contain the overlapping symbols of 10 elements. There is only one correct solution. $$\begin{array}{|l|l|}\hline 1 & 2 \\\\\hline 3 & 4 \\\\\hline\end{array}$$ Horizontal \(1-2:\) two-letter symbol for a metal used in ancient times \(3-4:\) two-letter symbol for a metal that burns in air and is found in Group \(5 \mathrm{A}\) Vertical \(1-3:\) two-letter symbol for a metalloid \(2-4:\) two-letter symbol for a metal used in U.S. coins single squares: All one-letter symbols 1: a colorful nonmetal 2: colorless, gaseous nonmetal 3: an element that makes fireworks green 4: an element that has medicinal uses Diagonal \(1-4:\) two-letter symbol for an element used in electronics \(2-3:\) two-letter symbol for a metal used with Zr to make wires for superconducting magnets This puzzle first appeared in Chemical \& Engineering News, p. \(86,\) December 14,1987 (submitted by S. J. Cyvin) and in Chem Matters, October 1988.

Which of the following is impossible? (a) silver foil that is \(1.2 \times 10^{-4} \mathrm{m}\) thick (b) a sample of potassium that contains \(1.784 \times\) \(10^{24}\) atoms (c) a gold coin of mass \(1.23 \times 10^{-3} \mathrm{kg}\) (d) \(3.43 \times 10^{-27}\) mol of \(S_{8}\) molecules

Identify two nonmetallic elements that have allotropes and describe the allotropes of each.

The recommended daily allowance (RDA) of iron for women \(19-30\) years old is 18 mg. How many moles is this? How many atoms?

Put the following elements in order from smallest to largest mass: (a) \(3.79 \times 10^{24}\) atoms Fe (b) \(19.921 \mathrm{mol} \mathrm{H}_{2}\) (c) 8.576 mol \(\mathrm{C}\) (d) 7.4 mol \(\mathrm{Si}\) (e) 9.221 mol \(\mathrm{Na}\) (f) \(4.07 \times 10^{24}\) atoms \(\mathrm{Al}\) (g) 9.2 mol \(\mathrm{Cl}_{2}\)

When a sample of phosphorus burns in air, the compound \(\mathrm{P}_{4} \mathrm{O}_{10}\) forms. One experiment showed that 0.744 g of phosphorus formed \(1.704 \mathrm{g}\) of \(\mathrm{P}_{4} \mathrm{O}_{10} .\) Use this information to determine the ratio of the atomic weights of phosphorus and oxygen (mass P/mass O). If the atomic weight of oxygen is assumed to be \(16.000,\) calculate the atomic weight of phosphorus.

Although carbon-12 is now used as the standard for atomic weights, this has not always been the case. Early attempts at classification used hydrogen as the standard, with the weight of hydrogen being set equal to 1.0000. Later attempts defined atomic weights using oxygen (with a weight of 16.0000 ). In each instance, the atomic weights of the other elements were defined relative to these masses. (To answer this question, you need more precise data on current atomic weights: \(\mathrm{H}, 1.00794 ;\) O, \(15.9994 .\)) (a) If \(\mathrm{H}=1.0000 \mathrm{u}\) was used as a standard for atomic weights, what would the atomic weight of oxygen be? What would be the value of Avogadro's number under these circumstances? (b) Assuming the standard is \(\mathrm{O}=16.0000\), determine the value for the atomic weight of hydrogen and the value of Avogadro's number.

A reagent occasionally used in chemical synthesis is sodium-potassium alloy. (Alloys are mixtures of metals, and Na-K has the interesting property that it is a liquid.) One formulation of the alloy (the one that melts at the lowest temperature) contains 68 atom percent \(\mathrm{K} ;\) that is, out of every 100 atoms, 68 are \(\mathrm{K}\) and 32 are \(\mathrm{Na}\). What is the mass percent of potassium in sodium-potassium alloy?

Write formulas for all of the compounds that can be made by combining the cations \(\mathrm{NH}_{4}^{+}\) and \(\mathrm{Ni}^{2+}\) with the anions \(\mathrm{CO}_{3}^{2-}\) and \(\mathrm{SO}_{4}^{2-}.\)

How many electrons are in a strontium atom (Sr)? Does an atom of Sr gain or lose electrons when forming an ion? How many electrons are gained or lost by the atom? When Sr forms an ion, the ion has the same number of electrons as which one of the noble gases?

Which of the following compounds has the highest mass percent of chlorine? (a) \(\mathrm{BCl}_{3}\) (b) \(\mathrm{AsCl}_{3}\) (c) \(\mathrm{GaCl}_{3}\) (d) \(\mathrm{AlCl}_{3}\) (e) \(\mathrm{PCl}_{3}\)

Which of the following samples has the largest number of ions? (a) \(1.0 \mathrm{g}\) of \(\mathrm{BeCl}_{2}\) (b) \(1.0 \mathrm{g}\) of \(\mathrm{MgCl}_{2}\) (c) 1.0 g of CaS (d) \(1.0 \mathrm{g}\) of \(\mathrm{SrCO}_{3}\) (e) \(1.0 \mathrm{g}\) of \(\mathrm{BaSO}_{4}\)

The structure of one of the bases in DNA, adenine, is shown here. Which represents the greater mass: \(40.0 \mathrm{g}\) of adenine or \(3.0 \times 10^{23}\) molecules of the compound?

Ionic and molecular compounds of the halogens. (a) What are the names of BaF \(_{2}, \mathrm{SiCl}_{4}\), and \(\mathrm{NiBr}_{2} ?\) (b) Which of the compounds in part (a) are ionic, and which are molecular? (c) Which has the largest mass, 0.50 mol of BaF \(_{2}\) 0.50 mol of \(\mathrm{SiCl}_{4},\) or 1.0 mol of \(\mathrm{NiBr}_{2} ?\)