Chapter 3

Calculate the total number of (a) atoms in one molecule of trinitrotoluene (TNT), \(\mathrm{CH}_{3} \mathrm{C}_{6} \mathrm{H}_{2}\left(\mathrm{NO}_{2}\right)_{3}\) (b) atoms in \(0.00102 \mathrm{mol} \mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{4} \mathrm{CH}_{2} \mathrm{OH}\) (c) \(\mathrm{F}\) atoms in \(1215 \mathrm{mol} \mathrm{C}_{2} \mathrm{HBr} \mathrm{ClF}_{3}\)

Determine the mass, in grams, of (a) \(7.34 \mathrm{mol} \mathrm{N}_{2} \mathrm{O}_{4}\) (b) \(3.16 \times 10^{24} \mathrm{O}_{2}\) molecules; (c) \(18.6 \mathrm{mol} \mathrm{CuSO}_{4} \cdot 5 \mathrm{H}_{2} \mathrm{O}\) (d) \(4.18 \times 10^{24}\) molecules of \(\mathrm{C}_{2} \mathrm{H}_{4}(\mathrm{OH})_{2}\)

The amino acid methionine, which is essential in human diets, has the molecular formula \(\mathrm{C}_{5} \mathrm{H}_{11} \mathrm{NO}_{2} \mathrm{S}\) Determine (a) its molecular mass; (b) the number of moles of \(\mathrm{H}\) atoms per mole of methionine; (c) the number of grams of \(C\) per mole of methionine; (d) the number of \(C\) atoms in 9.07 mol methionine.

Determine the number of moles of \(\mathrm{Br}_{2}\) in a sample consisting of (a) \(8.08 \times 10^{22} \mathrm{Br}_{2}\) molecules; (b) \(2.17 \times 10^{24}\) Br atoms; (c) 11.3 kg bromine; (d) \(2.65 \mathrm{L}\) liquid bromine \((d=3.10 \mathrm{g} / \mathrm{mL})\)

Without doing detailed calculations, explain which of the following has the greatest number of \(\mathrm{N}\) atoms (a) \(50.0 \mathrm{g}\) \(\mathrm{N}_{2} \mathrm{O} ;\) (b) \(17.0 \mathrm{g} \mathrm{NH}_{3} ;\) (c) \(150 \mathrm{mL}\) of liquid pyridine, \(\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{N}(d=0.983 \mathrm{g} / \mathrm{mL}) ;\) (d) \(1.0 \mathrm{mol} \mathrm{N}_{2}\)

Without doing detailed calculations, determine which of the following has the greatest number of \(S\) atoms (a) 0.12 mol of solid sulfur, \(S_{8} ;\) (b) 0.50 mol of gaseous \(\mathrm{S}_{2} \mathrm{O} ;(\mathrm{c}) 65 \mathrm{g}\) of gaseous \(\mathrm{SO}_{2} ;(\mathrm{d}) 75 \mathrm{mL}\) of liquid thiophene, \(\mathrm{C}_{4} \mathrm{H}_{4} \mathrm{S}(d=1.064 \mathrm{g} / \mathrm{mL})\)

Determine the number of moles of (a) \(\mathrm{N}_{2} \mathrm{O}_{4}\) in a \(115 \mathrm{g}\) sample (b) \(\mathrm{N}\) atoms in \(43.5 \mathrm{g}\) of \(\mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2}\) (c) \(\mathrm{N}\) atoms in a sample of \(\mathrm{C}_{7} \mathrm{H}_{5}\left(\mathrm{NO}_{2}\right)_{3}\) that has the same number of \(\mathrm{O}\) atoms as \(12.4 \mathrm{g} \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\)

The hemoglobin content of blood is about \(15.5 \mathrm{g} / 100 \mathrm{mL}\) blood. The molar mass of hemoglobin is about \(64,500 \mathrm{g} / \mathrm{mol},\) and there are four iron (Fe) atoms in a hemoglobin molecule. Approximately how many Fe atoms are present in the 6 Lof blood in a typical adult?

Explain which of the following statement(s) is (are) correct concerning glucose (blood sugar), \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\) (a) The percentages, by mass, of \(\mathrm{C}\) and \(\mathrm{O}\) are the same as in CO. (b) The ratio of \(\mathrm{C}: \mathrm{H}: \mathrm{O}\) atoms is the same as in dihydroxyacetone, \(\left(\mathrm{CH}_{2} \mathrm{OH}\right)_{2} \mathrm{CO}\) (c) The proportions, by mass, of \(C\) and \(O\) are equal. (d) The highest percentage, by mass, is that of H.

Explain which of the following statement(s) is (are) correct for sorbic acid, \(\mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{2},\) an inhibitor of mold and yeast. (a) It has a \(\mathrm{C}: \mathrm{H}:\) O mass ratio of 3: 4: 1 (b) It has the same mass percent composition as the aquatic herbicide, acrolein, \(\mathrm{C}_{3} \mathrm{H}_{4} \mathrm{O}\) (c) It has the same empirical formula as aspidinol, \(\mathrm{C}_{12} \mathrm{H}_{16} \mathrm{O}_{4},\) a drug used to kill parasitic worms. (d) It has four times as many \(\mathrm{H}\) atoms as \(\mathrm{O}\) atoms, but four times as much O as H by mass.

For the mineral torbernite, \(\mathrm{Cu}\left(\mathrm{UO}_{2}\right)_{2}\left(\mathrm{PO}_{4}\right)_{2} \cdot 8 \mathrm{H}_{2} \mathrm{O}\) determine (a) the total number of atoms in one formula unit (b) the ratio, by number, of \(\mathrm{H}\) atoms to \(\mathrm{O}\) atoms (c) the ratio, by mass, of \(\mathrm{Cu}\) to \(\mathrm{P}\) (d) the element present in the greatest mass percent (e) the mass required to contain \(1.00 \mathrm{g} \mathrm{P}\)

For the compound \(\operatorname{Ge}\left[\mathrm{S}\left(\mathrm{CH}_{2}\right)_{4} \mathrm{CH}_{3}\right]_{4},\) determine (a) the total number of atoms in one formula unit (b) the ratio, by number, of C atoms to H atoms (c) the ratio, by mass, of Ge to \(S\) (d) the number of \(g\) S in 1 mol of the compound (e) the number of \(C\) atoms in 33.10 g of the compound

Determine the mass percent \(\mathrm{H}\) in the hydrocarbon decane, \(\mathrm{C}_{10} \mathrm{H}_{22}\)

Determine the mass percent \(O\) in the mineral malachite, \(\mathrm{Cu}_{2}(\mathrm{OH})_{2} \mathrm{CO}_{3}\)

Determine the mass percent \(H\) in the hydrocarbon isooctane, \(\mathrm{C}\left(\mathrm{CH}_{3}\right)_{3} \mathrm{CH}_{2} \mathrm{CH}\left(\mathrm{CH}_{3}\right)_{2}\)

Determine the mass percent \(\mathrm{H}_{2} \mathrm{O}\) in the hydrate \(\mathrm{Cr}\left(\mathrm{NO}_{3}\right)_{3} \cdot 9 \mathrm{H}_{2} \mathrm{O}\)

Determine the mass percent of each of the elements in the antimalarial drug quinine, \(\mathrm{C}_{20} \mathrm{H}_{24} \mathrm{N}_{2} \mathrm{O}_{2}\)

Determine the mass percent of each of the elements in the fungicide copper(II) oleate, \(\mathrm{Cu}\left(\mathrm{C}_{18} \mathrm{H}_{33} \mathrm{O}_{2}\right)_{2}\)

Determine the percent, by mass, of the indicated element: (a) \(\mathrm{Pb}\) in tetraethyl lead, \(\mathrm{Pb}\left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{4},\) once extensively used as an additive to gasoline to prevent engine knocking (b) Fe in Prussian blue, \(\mathrm{Fe}_{4}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]_{3},\) a pigment used in paints and printing inks (c) \(\mathrm{Mg}\) in chlorophyll, \(\mathrm{C}_{55} \mathrm{H}_{72} \mathrm{MgN}_{4} \mathrm{O}_{5},\) the green pigment in plant cells

All of the following minerals are semiprecious or precious stones. Determine the mass percent of the indicated element. (a) \(\mathrm{Zr}\) in zircon, \(\mathrm{ZrSiO}_{4}\) (b) Be in beryl (emerald), \(\mathrm{Be}_{3} \mathrm{Al}_{2} \mathrm{Si}_{6} \mathrm{O}_{18}\) (c) Fe in almandine (garnet), \(\mathrm{Fe}_{3} \mathrm{Al}_{2} \mathrm{Si}_{3} \mathrm{O}_{12}\) (d) S in lazurite (lapis lazuli), \(\mathrm{Na}_{4} \mathrm{SSi}_{3} \mathrm{Al}_{3} \mathrm{O}_{12}\)

Without doing detailed calculations, arrange the following in order of increasing \(\% \mathrm{Cr},\) by mass, and explain your reasoning: \(\mathrm{CrO}, \mathrm{Cr}_{2} \mathrm{O}_{3}, \mathrm{CrO}_{2}, \mathrm{CrO}_{3}\)

Without doing detailed calculations, explain which of the following has the greatest mass percent of sulfur. \(\mathrm{SO}_{2}, \mathrm{S}_{2} \mathrm{Cl}_{2}, \mathrm{Na}_{2} \mathrm{S}, \mathrm{Na}_{2} \mathrm{S}_{2} \mathrm{O}_{3}, \mathrm{or} \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{SH}\)

Diethylene glycol, used to deice aircraft, is a carbonhydrogen-oxygen compound with \(45.27 \%\) C and \(9.50 \%\) H by mass. What is its empirical formula?

The food flavor enhancer monosodium glutamate (MSG) has the composition \(13.6 \%\) Na, \(35.5 \%\) C. \(4.8 \% \mathrm{H}, 8.3 \% \mathrm{N}, 37.8 \% \mathrm{O},\) by mass. What is the empirical formula of MSG?

Determine the empirical formula of (a) the rodenticide (rat killer) warfarin, which consists of \(74.01 \% \mathrm{C}\) \(5.23 \% \mathrm{H},\) and \(20.76 \%\) O, by mass; (b) the antibacterial agent sulfamethizole, which consists of \(39.98 \%\) C. \(3.73 \% \mathrm{H}, 20.73 \% \mathrm{N}, 11.84 \% \mathrm{O},\) and \(23.72 \% \mathrm{S},\) by mass.

Determine the empirical formula of (a) benzo-[a]pyrene, a suspected carcinogen found in cigarette smoke, consisting of \(95.21 \%\) C and \(4.79 \%\) H, by mass; (b) hexachlorophene, used in germicidal soaps, which consists of \(38.37 \%\) C \(, 1.49 \%\) H, \(52.28 \%\) Cl, and \(7.86 \%\) O by mass.

A compound of carbon and hydrogen consists of \(94.34 \% \mathrm{C}\) and \(5.66 \% \mathrm{H},\) by mass. The molecular mass of the compound is found to be 178 u. What is its molecular formula?

Selenium, an element used in the manufacture of photoelectric cells and solar energy devices, forms two oxides. One has \(28.8 \%\) O, by mass, and the other, 37.8\% O. What are the formulas of these oxides? Propose acceptable names for them.

Indigo, the dye for blue jeans, has a percent composition, by mass, of \(73.27 \%\) C \(, 3.84 \%\) H, \(10.68 \%\) N, and the remainder is oxygen. The molecular mass of indigo is 262.3 u. What is the molecular formula of indigo?

Adenine, a component of nucleic acids, has the mass percent composition: \(44.45 \%\) C \(, 3.73 \%\) H, \(51.82 \%\) N. Its molecular mass is 135.14 u. What is its molecular formula?

The element \(X\) forms the chloride \(X C l_{4}\) containing \(75.0 \% \mathrm{Cl},\) by mass. What is element \(\mathrm{X} ?\)

The element \(X\) forms the compound \(X O C l_{2}\) containing 59.6\% Cl. What is element X?

Two compounds of \(\mathrm{Cl}\) and \(\mathrm{X}\) are found to have molecular masses and \% Cl, by mass, as follows: 137 u, \(77.5 \% \mathrm{Cl} ; 208 \mathrm{u}, 85.1 \%\) Cl. What is element \(\mathrm{X} ?\) What is the formula for each compound?

A \(0.1888 \mathrm{g}\) sample of a hydrocarbon produces \(0.6260 \mathrm{g}\) \(\mathrm{CO}_{2}\) and \(0.1602 \mathrm{g} \mathrm{H}_{2} \mathrm{O}\) in combustion analysis. Its molecular mass is found to be 106 u. For this hydrocarbon, determine its (a) mass percent composition; (b) empirical formula; (c) molecular formula.

Para-cresol ( \(p\) -cresol) is used as a disinfectant and in the manufacture of herbicides. A 0.4039 g sample of this carbon-hydrogen-oxygen compound yields \(1.1518 \mathrm{g} \mathrm{CO}_{2}\) and \(0.2694 \mathrm{g} \mathrm{H}_{2} \mathrm{O}\) in combustion analysis. Its molecular mass is 108.1 u. For \(p\) -cresol, determine its (a) mass percent composition; (b) empirical formula; (c) molecular formula.

Dimethylhydrazine is a carbon-hydrogen-nitrogen compound used in rocket fuels. When burned in an excess of oxygen, a \(0.312 \mathrm{g}\) sample yields \(0.458 \mathrm{g} \mathrm{CO}_{2}\) and \(0.374 \mathrm{g} \mathrm{H}_{2} \mathrm{O}\). The nitrogen content of a \(0.486 \mathrm{g}\) sample is converted to \(0.226 \mathrm{g} \mathrm{N}_{2} .\) What is the empirical formula of dimethylhydrazine?

The organic solvent thiophene is a carbon-hydrogensulfur compound that yields \(\mathrm{CO}_{2}, \mathrm{H}_{2} \mathrm{O},\) and \(\mathrm{SO}_{2}\) when burned in an excess of oxygen. When subjected to combustion analysis, a \(1.3020 \mathrm{g}\) sample of thiophene produces \(2.7224 \mathrm{g} \mathrm{CO}_{2}, 0.5575 \mathrm{g} \mathrm{H}_{2} \mathrm{O},\) and \(0.9915 \mathrm{g} \mathrm{SO}_{2} .\) What is the empirical formula of thiophene?

Without doing detailed calculations, explain which of these compounds produces the greatest mass of \(\mathrm{H}_{2} \mathrm{O}\) when \(1.00 \mathrm{g}\) of the compound is burned in an excess of oxygen: \(\mathrm{CH}_{4}, \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}, \mathrm{C}_{10} \mathrm{H}_{8}, \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{OH}\)

A \(1.562 \mathrm{g}\) sample of the alcohol \(\mathrm{CH}_{3} \mathrm{CHOHCH}_{2} \mathrm{CH}_{3}\) is burned in an excess of oxygen. What masses of \(\mathrm{CO}_{2}\) and \(\mathrm{H}_{2} \mathrm{O}\) should be obtained?

Liquid ethyl mercaptan, \(\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{S},\) has a density of \(0.84 \mathrm{g} / \mathrm{mL} .\) Assuming that the combustion of this compound produces only \(\mathrm{CO}_{2}, \mathrm{H}_{2} \mathrm{O},\) and \(\mathrm{SO}_{2},\) what masses of each of these three products would be produced in the combustion of \(3.15 \mathrm{mL}\) of ethyl mercaptan?

Indicate the oxidation state of \(S\) in \(\left(\text { a) } \mathrm{SO}_{3}^{2-}\right.\) (b) \(\mathrm{S}_{2} \mathrm{O}_{3}^{2-} ;\) (c) \(\mathrm{S}_{2} \mathrm{O}_{8}^{2-} ;\) (d) \(\mathrm{HSO}_{4}^{-} ;\) (e) \(\mathrm{S}_{4} \mathrm{O}_{6}^{2-}\)

Chromium forms three principal oxides. Write appropriate formulas for these compounds in which the oxidation states of Cr are \(+3,+4,\) and \(+6,\) respectively.

Nitrogen forms five oxides in which its oxidation states are \(+1,+2,+3,+4,\) and \(+5,\) respectively. Write appropriate formulas for these compounds.

In many of its compounds, oxygen has an oxidation state of \(-2 .\) However, there are exceptions. What is the oxidation state of oxygen in each of the following compounds? (a) \(\mathrm{OF}_{2} ;\) (b) \(\mathrm{O}_{2} \mathrm{F}_{2} ;\) (c) \(\mathrm{CsO}_{2}\); (d) \(\mathrm{BaO}_{2}\)

Hydrogen and oxygen usually have oxidation states of +1 and \(-2,\) respectively, in their compounds. The following cases serve to remind us that there are exceptions. What are the oxidation states of the atoms in each of the following compounds? (a) \(\mathrm{MgH}_{2}\) (b) \(\mathrm{CsO}_{3} ;\) (c) HOF; (d) \(\mathrm{NaAlH}_{4}\)

Name these compounds: (a) \(\operatorname{SrO} ;\) (b) \(\mathrm{ZnS} ;\) (c) \(\mathrm{K}_{2} \mathrm{CrO}_{4}\) (d) \(\mathrm{Cs}_{2} \mathrm{SO}_{4} ;(\mathrm{e}) \mathrm{Cr}_{2} \mathrm{O}_{3} ;(\mathrm{f}) \mathrm{Fe}_{2}\left(\mathrm{SO}_{4}\right)_{3} ;(\mathrm{g}) \mathrm{Mg}\left(\mathrm{HCO}_{3}\right)_{2}\) (h) \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{HPO}_{4} ; \quad\) (i) \(\quad \mathrm{Ca}\left(\mathrm{HSO}_{3}\right)_{2} ; \quad(\mathrm{j}) \quad \mathrm{Cu}(\mathrm{OH})_{2}\) (k) \(\mathrm{HNO}_{3} ;\) (1) \(\mathrm{KClO}_{4} ;\) (m) \(\mathrm{HBrO}_{3} ;\) (n) \(\mathrm{H}_{3} \mathrm{PO}_{3}\).

Name these compounds: (a) \(\mathrm{Ba}\left(\mathrm{NO}_{3}\right)_{2} ;\) (b) \(\mathrm{HNO}_{2}\); (c) \(\operatorname{Cr} \mathrm{O}_{2} ;\) (d) \(\mathrm{KIO}_{3} ;\) (e) \(\mathrm{LiCN} ;\) (f) \(\mathrm{KIO} ;\) (g) \(\mathrm{Fe}(\mathrm{OH})_{2}\) (h) \(\mathrm{Ca}\left(\mathrm{H}_{2} \mathrm{PO}_{4}\right)_{2} ;\) (i) \(\mathrm{H}_{3} \mathrm{PO}_{4} ;\) (j) \(\mathrm{NaHSO}_{4} ;\) (k) \(\mathrm{Na}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\); (l) \(\mathrm{NH}_{4} \mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2} ;(\mathrm{m}) \mathrm{MgC}_{2} \mathrm{O}_{4} ;\) (n) \(\mathrm{Na}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\)

Assign suitable names to the compounds (a) \(\mathrm{CS}_{2}\) (b) \(\operatorname{SiF}_{4} ;\) (c) \(\operatorname{ClF}_{5} ;\) (d) \(\mathrm{N}_{2} \mathrm{O}_{5} ;\) (e) \(\mathrm{SF}_{6} ;\) (f) \(\mathrm{I}_{2} \mathrm{Cl}_{6}\).

Assign suitable names to the compounds (a) ICl; (b) \(\mathrm{ClF}_{3} ;\) (c) \(\mathrm{SF}_{4} ;\) (d) \(\mathrm{Br} \mathrm{F}_{5} ;\) (e) \(\mathrm{N}_{2} \mathrm{O}_{4} ;\) (f) \(\mathrm{S}_{4} \mathrm{N}_{4}\).

Write formulas for the compounds: (a) aluminum sulfate; (b) ammonium dichromate; (c) silicon tetrafluoride; (d) iron(III) oxide; (e) tricarbon disulfide; (f) cobalt(II) nitrate; (g) strontium nitrite; (h) hydrobromic acid; (i) iodic acid; (j) phosphorus dichloride trifluoride.