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- If 3.42 g of K2PtCl4 and 1.61 g of NH3 give 2.08 g of cispla-tin (Problem 3.81), what is the percent yield of the reaction?
Problem 83
Problem 84a
The reaction of tungsten hexachloride (WCl6) with bismuth gives hexatungsten dodecachloride (W6Cl12).
WCl6 + Bi → W6Cl12 + BiCl3 Unbalanced
(a) Balance the equation.
Problem 84b
The reaction of tungsten hexachloride (WCl6) with bismuth gives hexatungsten dodecachloride (W6Cl12).
WCl6 + Bi → W6Cl12 + BiCl3 Unbalanced
(b) How many grams of bismuth react with 150.0 g of WCl6?
Problem 84c
The reaction of tungsten hexachloride (WCl6) with bismuth gives hexatungsten dodecachloride (W6Cl12).
WCl6 + Bi → W6Cl12 + BiCl3 Unbalanced
(c) When 228 g of WCl6 react with 175 g of Bi, how much W6Cl12 is formed based on the limiting reactant?
Problem 85a
Sodium borohydride, NaBH4, a substance used in the synthesis of many pharmaceutical agents, can be prepared by reaction of NaH with B2H6 according to the equation 2 NaH + B2H6 → 2 NaBH4
(a) How many grams of NaBH4 can be prepared by reaction between 8.55 g of NaH and 6.75 g of B2H6?
Problem 85b
Sodium borohydride, NaBH4, a substance used in the synthesis of many pharmaceutical agents, can be prepared by reaction of NaH with B2H6 according to the equation 2 NaH + B2H6 → 2 NaBH4
(b) Which reactant is limiting, and how many grams of the excess reactant will be left over?
- Urea, a substance commonly used as a fertilizer, has the for-mula CH4N2O. What is its percent composition by mass?
Problem 86
Problem 87a
Calculate the mass percent composition of each of the following substances. (a) Malachite, a copper-containing mineral: Cu2(OH)2CO3
Problem 87b
Calculate the mass percent composition of each of the following substances. (b) Acetaminophen, a headache remedy: C8H9NO2
Problem 87c
Calculate the mass percent composition of each of the following substances. (c) Prussian blue, an ink pigment: Fe4[Fe(CN)6]3
Problem 88b
What are the empirical formulas of substances with the following mass percent compositions? (b) Ilmenite (a titanium-containing ore): 31.63% O, 31.56% Ti, 36.81% Fe
Problem 88c
What are the empirical formulas of substances with the following mass percent compositions? (c) Sodium thiosulfate (photographic 'fixer'): 30.36% O, 29.08% Na, 40.56% S
- Ferrocene, a substance proposed for use as a gasoline additive, has the percent composition 5.42% H, 64.56% C, and 30.02% Fe. What is the empirical formula of ferrocene?
Problem 89
- What is the empirical formula of stannous fluoride, the first fluoride compound added to toothpaste to protect teeth against decay? Its mass percent composition is 24.25% F, 75.75% Sn.
Problem 90
Problem 91b
What are the empirical formulas of each of the following substances? (b) Magnetite, a naturally occurring magnetic mineral: 72.36% Fe, 27.64% O
Problem 91c
What are the empirical formulas of each of the following substances? (c) Zircon, a mineral from which cubic zirconia is made: 34.91% O, 15.32% Si, 49.77% Zr
- An unknown liquid is composed of 5.57% H, 28.01% Cl, and 66.42% C. The molecular weight found by mass spectrometry is 126.58. What is the molecular formula of the compound?
Problem 92
- An unknown liquid is composed of 34.31% C, 5.28% H, and 60.41% I. The molecular weight found by mass spectrometry is 210.06. What is the molecular formula of the compound?
Problem 93
Problem 96
Cytochrome c is an iron-containing enzyme found in the cells of all aerobic organisms. If cytochrome c is 0.43% Fe by mass, what is its minimum molecular weight?
- Nitrogen fixation in the root nodules of peas and other leguminous plants is carried out by the molybdenum-containing enzyme nitrogenase. What is the molecular mass of nitrogenase if the enzyme contains two molybdenum atoms and is 0.0872% Mo by mass?
Problem 97
- Disilane, Si2Hx, is analyzed and found to contain 90.28% silicon by mass. What is the value of x?
Problem 98
- A certain metal sulfide, MS2, is used extensively as a high-temperature lubricant. If MS2 is 40.06% sulfur by mass, what is the identity of the metal M?
Problem 99
- Combustion analysis of a 31.472 mg sample of the widely used flame retardant Decabrom gave 1.444 mg of CO2. Is the molecular formula of Decabrom C12Br10 or C12Br10O?
Problem 100
- The stimulant amphetamine contains only carbon, hydrogen, and nitrogen. Combustion analysis of a 42.92 mg sample of amphetamine gives 37.187 mg of H2O and 125.75 mg of CO2. If the molar mass of amphetamine is less than 160 g/mol, what is its molecular formula?
Problem 101
Problem 101a
Heating elemental cesium and platinum together for two days at 973 K gives a dark red ionic compound that is 57.67% Cs and 42.33% Pt. (a) What is the empirical formula of the compound?
- Describe the path of a neutral molecule in the mass spectrometer. Why is ionization a necessary first step?
Problem 102
- Why are high precision and accuracy in molecular mass measurement needed for identifying the formula of molecules made in the lab?
Problem 103
- The mass of an organic compound was found by mass spectrometry to be 58.07746. Is the sample C4H10, C3H6O, or C2H6N2? Exact masses of elements are: 1.007825 (1H); 12.00000 (12C); 14.003074 (14N); 15.994915 (16O).
Problem 105
Problem 106a
(a) Combustion analysis of 50.0 mg of benzene, a commonly used solvent composed of carbon and hydrogen, gives 34.6 mg of H2O and 169.2 mg of CO2. What is the empirical formula of benzene?
Problem 106b
b) Given the mass spectrum of benzene, identify the molecular weight and give the molecular formula.