Answer: Many cereals are made with high moisture content

What if you were offered $1 million to count from 1 to 6 3 1023 at a rate of one number each second? Determine your hourly wage. Would you do it? Could you do it?

What if you discovered Avogadros number was not 6.02 3 1023 but 3.01 3 1023? Would this affect the relative masses given on the periodic table? If so, how? If not, why not?

One part of the problem solving strategy for empirical formula determination is to base the calculation on 100 grams of compound. What if you chose a mass other that 100 g? Would this work? What if you chose to base the calculation on 100 moles of compound? Would this work?

What if a friend was balancing chemical equations by changing the values of the subscripts instead of using the coefficients? How would you explain to your friend that this was the wrong thing to do?

One part of the problem solving strategy for balancing chemical equations is starting with the most complicated molecule. What if you started with a different molecule? Could you still eventually balance the chemical equation? How would this approach be different from the suggested technique?

Your lab partner has made the observation that you always take the mass of chemicals in lab, but then use mole ratios to balance the equation. Why not use the masses in the equation?, your partner asks. What if your lab partner decided to balance equations by using masses as coefficients? Is this even possible? Why or why not?

The following are actual student responses to the question: Why is it necessary to balance chemical equations? a. The chemicals will not react until you have added the correct mole ratios. b. The correct products will not be formed unless the right amount of reactants have been added. c. A certain number of products cannot be formed without a certain number of reactants. d. The balanced equation tells you how much reactant you need and allows you to predict how much product you will make. e. A mole-to-mole ratio must be established for the reaction to occur as written. What is the best choice? For those you did not choose, explain why they are incorrect. State the fundamental reason why an equation for a reaction must be balanced

Consider the equation A 1 2B n AB2. Imagine that 10 moles of A is reacted with 26 moles of B. Use a scale from 0 to 10 to express your level of agreement with each of the following statements. Justify and discuss your responses. a. There will be some As left over. b. There will be some Bs left over. c. Because of leftover As, some A2 molecules will be formed. d. Because of leftover Bs, some B2 molecules will be formed. e. Even if A is not limiting, A2 molecules will be formed. f. Even if B is not limiting, B2 molecules will be formed. g. Along with the molecule AB2, molecules with the formula AxBy (other than AB2) will be formed

What information do we get from a formula? From an equation?

A sample of liquid heptane (C7H16) weighing 11.50 g is reacted with 1.300 moles of oxygen gas. The heptane is burned completely (heptane reacts with oxygen to form both carbon monoxide and water and carbon dioxide and water). After the reaction is complete, the amount of gas present is 1.050 moles (assume that all of the water formed is liquid). a. How many moles of CO are produced? b. How many moles of CO2 are produced? c. How many moles of O2 are left over?

Nitrogen (N2) and hydrogen (H2) react to form ammonia (NH3). Consider the mixture of N2( ) and H2( ) in a closed container as illustrated: Assuming that the reaction goes to completion, draw a representation of the product mixture. Explain how you arrived at this representation

For the preceding question, which of the following equations best represents the reaction? a. 6N2 1 6H2 n 4NH3 1 4N2 b. N2 1 H2 n NH3 c. N 1 3H n NH3 d. N2 1 3H2 n 2NH3 e. 2N2 1 6H2 n 4NH3 Justify your choice. For those you did not choose, explain why they are incorrect.

You know that chemical A reacts with chemical B. You react 10.0 g A with 10.0 g B. What information do you need to have to determine the amount of product that will be produced? Explain.

A kerosene lamp has a mass of 1.5 kg. You put 0.5 kg of kerosene in the lamp. You burn all the kerosene until the lamp has a mass of 1.5 kg. What is the mass of the gases that are given off? Explain.

Consider an iron bar on a balance as shown. 75.0 g As the iron bar rusts, which of the following is true? Explain your answer. a. The balance will read less than 75.0 g. b. The balance will read 75.0 g. c. The balance will read greater than 75.0 g. d. The balance will read greater than 75.0 g, but if the bar is removed, the rust scraped off, and the bar replaced, the balance will read 75.0 g

You may have noticed that water sometimes drips from an exhaust pipe of a car as it is running. Is this evidence that there is at least a small amount of water originally present in the gasoline? Explain.

What is the mass of the product? a. less than 20 g d. exactly 120 g b. between 20 and 100 g e. more than 120 g c. between 100 and 120 g

What is true about the chemical properties of the product? a. The properties are more like those of chemical A. b. The properties are more like those of chemical B. c. The properties are an average of those of chemical A and chemical B. d. The properties are not necessarily like those of either chemical A or chemical B. Justify your choice. For those you did not choose, explain why they are incorrect.

What is the difference between the empirical and molecular formulas of a compound? Can they ever be the same? Explain.

Atoms of three different elements are represented by , , and . Which compound is left over when three molecules of and three molecules of react to form and ?

One way of determining the empirical formula is to burn a compound in air and weigh the amounts of carbon dioxide and water given off. For what types of compounds does this work? Explain the assumptions that are made. Why is the formula an empirical formula and not necessarily a molecular formula?

In chemistry, what is meant by the term mole? What is the importance of the mole concept?

Which (if any) of the following is true regarding the limiting reactant in a chemical reaction? a. The limiting reactant has the lowest coefficient in a balanced equation. b. The limiting reactant is the reactant for which you have the fewest number of moles. c. The limiting reactant has the lowest ratio of moles available/coefficient in the balanced equation. d. The limiting reactant has the lowest ratio of coefficient in the balanced equation/moles available. Justify your choice. For those you did not choose, explain why they are incorrect

Consider the equation 3A 1 B n C 1 D. You react 4 moles of A with 2 moles of B. Which of the following is true? a. The limiting reactant is the one with the higher molar mass. b. A is the limiting reactant because you need 6 moles of A and have 4 moles. c. B is the limiting reactant because you have fewer moles of B than A. d. B is the limiting reactant because three A molecules react with each B molecule. e. Neither reactant is limiting. Justify your choice. For those you did not choose, explain why they are incorrect.

Chlorine exists mainly as two isotopes, 37Cl and 35Cl. Which is more abundant? How do you know?

According to the law of conservation of mass, mass cannot be gained or destroyed in a chemical reaction. Why cant you simply add the masses of two reactants to determine the total mass of product?

The atomic mass of boron (B) is given in the periodic table as 10.81, yet no single atom of boron has a mass of 10.81 u. Explain.

Why is the actual yield of a reaction often less than the theoretical yield?

An element X has five major isotopes, which are listed below along with their abundances. Calculate the average atomic mass, and identify the element.

The stable isotopes of iron are 54Fe, 56Fe, 57Fe, and 58Fe. The mass spectrum of iron looks like the following: Relative number of atoms 0 Mass number 54 56 57 58 20 40 60 80 100 5.85 91.75 2.12 0.28 Use the data on the mass spectrum to estimate the average atomic mass of iron and compare it with the value given in the table inside the front cover of this book.

The element silver (Ag) has two naturally occurring isotopes: 109Ag and 107Ag with a mass of 106.905 u. Silver consists of 51.82% 107Ag and has an average atomic mass of 107.868 u. Calculate the mass of 109Ag.

The element europium exists in nature as two isotopes: 151Eu has a mass of 150.9196 u, and 153Eu has a mass of 152.9209 u. The average atomic mass of europium is 151.96 u. Calculate the relative abundance of the two europium isotopes.

The element rhenium (Re) has two naturally occurring isotopes, 185Re and 187Re, with an average atomic mass of 186.207 u. Rhenium is 62.60% 187Re, and the atomic mass of 187Re is 186.956 u. Calculate the mass of 185Re

An element consists of 1.40% of an isotope with mass 203.973 u, 24.10% of an isotope with mass 205.9745 u, 22.10% of an isotope with mass 206.9759 u, and 52.40% of an isotope with mass 207.9766 u. Calculate the average atomic mass and identify the element.

The mass spectrum of bromine (Br2) consists of three peaks with the following relative sizes: Mass (u) Relative Size 157.84 0.2534 159.84 0.5000 161.84 0.2466 How do you interpret these data, and what is the relative abundance of the bromine isotopes?

Naturally occurring tellurium (Te) has the following isotopic abundances: Isotope Abundance Mass (u) 120Te 0.09% 119.90 122Te 2.46% 121.90 123Te 0.87% 122.90 124Te 4.61% 123.90 125Te 6.99% 124.90 126Te 18.71% 125.90 128Te 31.79% 127.90 130Te 34.48% 129.91 Draw the mass spectrum of H2Te, assuming that the only hydrogen isotope present is 1H (mass 1.008).

Gallium arsenide (GaAs) has gained widespread use in semiconductor devices that interconvert light and electrical signals in fiber-optic communications systems. Gallium consists of 60.% 69Ga and 40.% 71Ga. Arsenic has only one naturally occurring isotope, 75As. Gallium arsenide is a polymeric material, but its mass spectrum shows fragments with formulas GaAs and Ga2As2. What would the distribution of peaks look like for these two fragments?

Ascorbic acid, or vitamin C (C6H8O6), is an essential vitamin. It cannot be stored by the body and must be present in the diet. What is the molar mass of ascorbic acid? Vitamin C tablets are taken as a dietary supplement. If a typical tablet contains 500.0 mg vitamin C, what amount (moles) of vitamin C is contained in 10 tablets? What number of vitamin C molecules are in 8 tablets?

The molecular formula of acetylsalicylic acid (aspirin), one of the most commonly used pain relievers, is C9H8O4. a. Calculate the molar mass of aspirin. b. A typical aspirin tablet contains 500. mg C9H8O4. What amount (moles) of C9H8O4 molecules and what number of molecules of acetylsalicylic acid are in a 500.-mg tablet?

Complete the following table. Mass of Sample Moles of Sample Molecules in Sample Total Atoms in Sample 4.24 g C6H6 ________ ________ ________ ________ 0.224 mol H2O ________ ________ ________ ________ 2.71 3 1022 molecules CO2 ________ ________ ________ ________ 3.35 3 1022 total atoms in CH3OH sample

What amount (moles) is represented by each of these samples? a. 20.0 mg caffeine, C8H10N4O2 b. 2.72 3 1021 molecules of ethanol, C2H5OH c. 1.50 g of dry ice, CO2

How many atoms of nitrogen are present in 5.00 g of each of the following? a. glycine, C2H5O2N c. calcium nitrate b. magnesium nitride d. dinitrogen tetroxide

Consider the following gas samples: 4.0 g of hydrogen gas, 4.0 g of helium gas, 1.0 mole of fluorine gas, 44.0 g of carbon dioxide gas, and 146 g of sulfur hexafluoride gas. Arrange the gas samples in order of increasing number of total atoms present.

Aspartame is an artificial sweetener that is 160 times sweeter than sucrose (table sugar) when dissolved in water. It is marketed as NutraSweet. The molecular formula of aspartame is C14H18N2O5. a. Calculate the molar mass of aspartame. b. How many moles of molecules are in 10.0 g of aspartame? c. What is the mass in grams of 1.56 moles of aspartame? d. How many molecules are in 5.0 mg of aspartame? e. How many atoms of nitrogen are in 1.2 g of aspartame? f. What is the mass in grams of 1.0 3 109 molecules of aspartame? g. What is the mass in grams of one molecule of aspartame?

Chloral hydrate (C2H3Cl3O2) is a drug formerly used as a sedative and hypnotic. It is the compound used to make Mickey Finns in detective stories. a. Calculate the molar mass of chloral hydrate. b. How many moles of C2H3Cl3O2 molecules are in 500.0 g of chloral hydrate? c. What is the mass in grams of 2.0 3 1022 mol chloral hydrate? d. How many chlorine atoms are in 5.0 g chloral hydrate? e. What mass of chloral hydrate would contain 1.0 g Cl? f. What is the mass

In the spring of 1984, concern arose over the presence of ethylene dibromide, or EDB, in grains and cereals. EDB has the molecular formula C2H4Br2 and until 1984 was commonly used as a plant fumigant. The federal limit for EDB in finished cereal products is 30.0 parts per billion (ppb), where 1.0 ppb 5 1.0 3 1029 g of EDB for every 1.0 g of sample. How many molecules of EDB are in 1.0 lb of flour if 30.0 ppb of EDB is present?

Anabolic steroids are performance enhancement drugs whose use has been banned from most major sporting activities. One anabolic steroid is fluoxymesterone (C20H29FO3). Calculate the percent composition by mass of fluoxymesterone.

Calculate the percent composition by mass of the following compounds that are important starting materials for synthetic polymers: a. C3H4O2 (acrylic acid, from which acrylic plastics are made) b. C4H6O2 (methyl acrylate, from which Plexiglas is made) c. C3H3N (acrylonitrile, from which Orlon is made)

In 1987 the first substance to act as a superconductor at a temperature above that of liquid nitrogen (77 K) was discovered. The approximate formula of this substance is YBa2Cu3O7. Calculate the percent composition by mass of this material

Arrange the following substances in order of increasing mass percent of carbon. a. caffeine, C8H10N4O2 b. sucrose, C12H22O11 c. ethanol, C2H5OH

The percent by mass of nitrogen for a compound is found to be 46.7%. Which of the following could be this species? N O

Vitamin B12, cyanocobalamin, is essential for human nutrition. It is concentrated in animal tissue but not in higher plants. Although nutritional requirements for the vitamin are quite low, people who abstain completely from animal products may develop a deficiency anemia. Cyanocobalamin is the form used in vitamin supplements. It contains 4.34% cobalt by mass. Calculate the molar mass of cyanocobalamin, assuming that there is one atom of cobalt in every molecule of cyanocobalamin

Fungal laccase, a blue protein found in wood-rotting fungi, is 0.390% Cu by mass. If a fungal laccase molecule contains four copper atoms, what is the molar mass of fungal laccase?

Portland cement acts as the binding agent in concrete. A typical Portland cement has the following composition: Formula Name Mass Percent Ca3SiO5 Tricalcium silicate 50. Ca2SiO4 Dicalcium silicate 25 Ca3Al2O6 Tricalcium aluminate 12 Ca2AlFeO5 Calcium aluminoferrite 8.0 CaSO4 ? 2H2O Calcium sulfate dihydrate 3.5 Other substances, mostly MgO 1.5 Assuming that the impurities contain no Ca, Al, or Fe, calculate the mass percent of these elements in this Portland cement.

Express the composition of each of the following compounds as the mass percent of its elements. a. formaldehyde, CH2O b. glucose, C6H12O6 c. acetic acid, HC2H3O2 Considering your answers, which type of formula empirical or molecularcan be obtained from elemental analysis that gives mass percent composition? Explain.

Give the empirical formula of each of these compounds. a. c. d. b. O N C H P

Determine the molecular formulas to which the following empirical formulas and molar masses pertain. a. SNH (188.35 g/mol) b. NPCl2 (347.64 g/mol) c. CoC4O4 (341.94 g/mol) d. SN (184.32 g/mol)

A sample of urea contains 1.121 g N, 0.161 g H, 0.480 g C, and 0.640 g O. What is the empirical formula of urea?

There are two binary compounds of mercury and oxygen. Heating either of them results in the decomposition of the compound, with oxygen gas escaping into the atmosphere while leaving a residue of pure mercury. Heating 0.6498 g of one of the compounds leaves a residue of 0.6018 g. Heating 0.4172 g of the other compound results in a mass loss of 0.016 g. Determine the empirical formula of each compound.

The compound adrenaline contains 56.79% C, 6.56% H, 28.37% O, and 8.28% N by mass. What is the empirical formula of adrenaline?

The most common form of nylon (nylon-6) is 63.68% carbon, 12.38% nitrogen, 9.80% hydrogen, and 14.14% oxygen. Calculate the empirical formula for nylon-6.

One of the components that make up common table sugar is fructose, a compound that contains only carbon, hydrogen, and oxygen. Complete combustion of 1.50 g of fructose produced 2.20 g of carbon dioxide and 0.900 g of water. What is the empirical formula of fructose?

A compound contains only carbon, hydrogen, nitrogen, and oxygen. Combustion of 0.157 g of the compound produced 0.213 g of CO2 and 0.0310 g of H2O. In another experiment, 0.103 g of the compound produced 0.0230 g of NH3. What is the empirical formula of the compound? Hint: Combustion involves reacting with excess O2. Assume that all the carbon ends up in CO2 and all the hydrogen ends up in H2O. Also assume that all the nitrogen ends up in the NH3 in the second experiment.

Maleic acid is an organic compound composed of 41.39% C, 3.47% H, and the rest oxygen. If 0.129 mole of maleic acid has a mass of 15.0 g, what are the empirical and molecular formulas of maleic acid?

Determine the molecular formula of a compound that contains 26.7% P, 12.1% N, and 61.2% Cl, and has a molar mass of 580 g/mol.

Terephthalic acid is an important chemical used in the manufacture of polyesters and plasticizers. It contains only C, H, and O. Combustion of 19.81 mg terephthalic acid produces 41.98 mg CO2 and 6.45 mg H2O. If 0.250 mole of terephthalic acid has a mass of 41.5 g, determine the molecular formula of terephthalic acid.

A compound contains only carbon, hydrogen, and oxygen. Combustion of 10.68 mg of the compound yields 16.01 mg CO2 and 4.37 mg H2O. The molar mass of the compound is 176.1 g/mol. What are the empirical and molecular formulas of the compound?

ABS plastic is a tough, hard plastic used in applications requiring shock resistance (See Chapter 21). The polymer consists of three monomer units: acrylonitrile (C3H3N), butadiene (C4H6), and styrene (C8H8). a. A sample of ABS plastic contains 8.80% N by mass. It took 0.605 g of Br2 to react completely with a 1.20-g sample of ABS plastic. Bromine reacts 1;1 (by moles) with the butadiene molecules in the polymer and nothing else. What is the percent by mass of acrylonitrile and butadiene in this polymer? b. What are the relative numbers of each of the monomer units in this polymer?

The reaction of an element X with element Y is represented in the following diagram. Which of the equations best describes this reaction? Y X a. 3X 1 8Y n X3Y8 b. 3X 1 6Y n X3Y6 c. X 1 2Y n XY2 d. 3X 1 8Y n 3XY2 1 2Y

Silicon is produced for the chemical and electronics industries by the following reactions. Give the balanced equation for each reaction. Electric a. SiO2(s) 1 C(s) 88888888n Si2(s) 1 CO(g) arc furnace b. Silicon tetrachloride is reacted with very pure magnesium, producing silicon and magnesium chloride. c. Na2SiF6(s) 1 Na(s) 88n Si(s) 1 NaF(s)

Give the balanced equation for each of the following chemical reactions. a. Glucose (C6H12O6) reacts with oxygen gas to produce gaseous carbon dioxide and water vapor.b. Solid iron(III) sulfide reacts with gaseous hydrogen chloride to form solid iron(III) chloride and hydrogen sulfide gas. c. Carbon disulfide liquid reacts with ammonia gas to produce hydrogen sulfide gas and solid ammonium thiocyanate (NH4SCN)

Iron oxide ores, commonly a mixture of FeO and Fe2O3, are given the general formula Fe3O4. They yield elemental iron when heated to a very high temperature with either carbon monoxide or elemental hydrogen. Balance the following equations for these processes: Fe3O4 1s2 1 H2 1g2 h Fe1s2 1 H2O1g2 Fe3O4 1s2 1 CO1g2 h Fe1s2 1 CO2 1g2

Balance the following equations representing combustion reactions: a. b. (l) ( + + g) H C O (g) (g) (g) ( + + g) ( (g) g) c. C12H22O11 1s2 1 O2 1g2 S CO2 1g2 1 H2O1g2 d. Fe1s2 1 O2 1g2 S Fe2O3 1s2 e. FeO1s2 1 O2 1g2 S Fe2O3 1s2

Give the balanced equation for each of the following. a. The combustion of ethanol (C2H5OH) forms carbon dioxide and water vapor. A combustion reaction refers to a reaction of a substance with oxygen gas. b. Aqueous solutions of lead(II) nitrate and sodium phosphate are mixed, resulting in the precipitate formation of lead(II) phosphate with aqueous sodium nitrate as the other product

Balance the following equations. a. Cr(s) 1 S8(s) 888n Cr2S3(s) Heat b. NaHCO3(s) 888n Na2CO3(s) 1 CO2(g) 1 H2O(g) Heat c. KClO3(s) 888n KCl(s) 1 O2(g) d. Eu(s) 1 HF(g) 888n EuF3(s) 1 H2(g)

Balance each of the following chemical equations. a. KO2(s) 1 H2O(l) n KOH(aq) 1 O2(g) 1 H2O2(aq) b. Fe2O3(s) 1 HNO3(aq) n Fe(NO3)3(aq) 1 H2O(l) c. NH3(g) 1 O2(g) n NO(g) 1 H2O(g) d. PCl5(l) 1 H2O(l) n H3PO4(aq) 1 HCl(g) e. CaO(s) 1 C(s) n CaC2(s) 1 CO2(g) f. MoS2(s) 1 O2(g) n MoO3(s) 1 SO2(g) g. FeCO3(s) 1 H2CO3(aq) n Fe(HCO3)2(aq)

The reusable booster rockets of the U.S. space shuttle use a mixture of aluminum and ammonium perchlorate for fuel. A possible equation for this reaction is 3Al(s) 1 3NH4ClO4(s) 88n Al2O3(s) 1 AlCl3(s) 1 3NO(g) 1 6H2O(g)What mass of NH4ClO4 should be used in the fuel mixture for every kilogram of Al?

One of relatively few reactions that takes place directly between two solids at room temperature is Ba1OH2 2 # 8H2O1s2 1 NH4SCN1s2 h Ba1SCN2 2 1s2 1 H2O1l2 1 NH3 1g2 In this equation, the ? 8H2O in Ba(OH)2 ? 8H2O indicates the presence of eight water molecules. This compound is called barium hydroxide octahydrate. a. Balance the equation. b. What mass of ammonium thiocyanate (NH4SCN) must be used if it is to react completely with 6.5 g barium hydroxide octahydrate?

Elixirs such as Alka-Seltzer use the reaction of sodium bicarbonate with citric acid in aqueous solution to produce a fizz: 3NaHCO3 1aq2 1 C6H8O7 1aq2 h 3CO2 1g2 1 3H2O1l2 1 Na3C6H5O7 1aq2 a. What mass of C6H8O7 should be used for every 1.0 3 102 mg NaHCO3? b. What mass of CO2(g) could be produced from such a mixture?

Nitric acid is produced commercially by the Ostwald process. The three steps of the Ostwald process are shown in the following equations: 4NH3(g) 1 5O2(g) 88n 4NO(g) 1 6H2O(g) 2NO(g) 1 O2(g) 88n 2NO2(g) 3NO2(g) 1 H2O(l) 88n 2HNO3(aq) 1 NO(g) What mass of NH3 must be used to produce 1.0 3 106 kg of HNO3 by the Ostwald process, assuming 100% yield in each reaction and assuming the NO produced in the third stage is not recycled?

Over the years, the thermite reaction has been used for welding railroad rails, in incendiary bombs, and to ignite solid-fuel rocket motors. The reaction is Fe2O3(s) 1 2Al(s) 88n 2Fe(l) 1 Al2O3(s) What masses of iron(III) oxide and aluminum must be used to produce 15.0 g of iron? What is the maximum mass of aluminum oxide that could be produced?

The reaction between potassium chlorate and red phosphorus takes place when you strike a match on a matchbox. If you were to react 52.9 g of potassium chlorate (KClO3) with excess red phosphorus, what mass of tetraphosphorus decoxide (P4O10) could be produced? KClO3(s) 1 P4(s) 88n P4O10(s) 1 KCl(s) (unbalanced)

The space shuttle environmental control system handled excess CO2 (which the astronauts breathe out; it is 4.0% by mass of exhaled air) by reacting it with lithium hydroxide (LiOH) pellets to form lithium carbonate (Li2CO3) and water. If there were seven astronauts on board the shuttle, and each exhales 20. L of air per minute, how long could clean air be generated if there were 25,000 g of LiOH pellets available for each shuttle mission? Assume the density of air is 0.0010 g/mL.

Bacterial digestion is an economical method of sewage treatment. The reaction Bacteria 5CO2(g) 1 55NH4 1(aq) 1 76O2(g) 888888n C5H7O2N(s) 1 54NO2 2(aq) 1 52H2O(l) 1 109H1(aq) Bacterial tissue is an intermediate step in the conversion of the nitrogen in organic compounds into nitrate ions. How much bacterial tissue is produced in a treatment plant for every 1.0 3 104 kg of wastewater containing 3.0% NH4 1 ions by mass? Assume that 95% of the ammonium ions are consumed by the bacteria.

Phosphorus can be prepared from calcium phosphate by the following reaction: 2Ca3(PO4)2(s) 1 6SiO2(s) 1 10C(s) 88n 6CaSiO3(s) 1 P4(s) 1 10CO(g) Phosphorite is a mineral that contains Ca3(PO4)2 plus other non-phosphorus-containing compounds. What is the maximum amount of P4 that can be produced from 1.0 kg of phosphorite if the phosphorite sample is 75% Ca3(PO4)2 by mass? Assume an excess of the other reactants.

In the production of printed circuit boards for the electronics industry, a 0.60-mm layer of copper is laminated onto an insulating plastic board. Next, a circuit pattern made of a chemically resistant polymer is printed on the board. The unwanted copper is removed by chemical etching and the protective polymer is finally removed by solvents. One etching reaction is Cu(NH3)4Cl2(aq) 1 4NH3(aq) 1 Cu(s) 88n 2Cu(NH3)4Cl(aq) A plant needs to manufacture 10,000 printed circuit boards, each 8.0 3 16.0 cm in area. An average of 80.% of the copper is removed from each board (density of copper 5 8.96 g/cm3). What masses of Cu(NH3)4Cl2 and NH3 are needed to do this? Assume 100% yield.

Consider the reaction between NO(g) and O2(g) represented below. NO NO2 O2 What is the balanced equation for this reaction and what is the limiting reactant?

Consider the following reaction: 4NH3(g) 1 5O2(g) 88n 4NO(g) 1 6H2O(g) If a container were to have 10 molecules of O2 and 10 molecules of NH3 initially, how many total molecules (reactants plus products) would be present in the container after this reaction goes to completion?

Hydrogen peroxide is used as a cleaning agent in the treatment of cuts and abrasions for several reasons. It is an oxidizing agent that can directly kill many microorganisms; it decomposes upon contact with blood, releasing elemental oxygen gas (which inhibits the growth of anaerobic microorganisms); and it foams upon contact with blood, which provides a cleansing action. In the laboratory, small quantities of hydrogen peroxide can be prepared by the action of an acid on an alkaline earth metal peroxide, such as barium peroxide: BaO2(s) 1 2HCl(aq) 88n H2O2(aq) 1 BaCl2(aq) What amount of hydrogen peroxide should result when 1.50 g of barium peroxide is treated with 88.0 mL of hydrochloric acid solution containing 0.0272 g of HCl per mL? What mass of which reagent is left unreacted?

Silver sulfadiazine burn-treating cream creates a barrier against bacterial invasion and releases antimicrobial agents directly into the wound. If 25.0 g of Ag2O is reacted with 50.0 g of C10H10N4SO2, what mass of silver sulfadiazine (AgC10H9N4SO2) can be produced, assuming 100% yield? Ag2O(s) 1 2C10H10N4SO2(s) 88n 2AgC10H9N4SO2(s) 1 H2O(l)

Bornite (Cu3FeS3) is a copper ore used in the production of copper. When heated, the following reaction occurs: 2Cu3FeS3(s) 1 7O2(g) 88n 6Cu(s) 1 2FeO(s) 1 6SO2(g) If 2.50 metric tons of bornite is reacted with excess O2 and the process has an 86.3% yield of copper, how much copper is produced?

DDT, an insecticide harmful to fish, birds, and humans, is produced by the following reaction: 2C6H5Cl 1 C2HOCl3 88n C14H9Cl5 1 H2O Chlorobenzene Chloral DDT In a government lab, 1142 g of chlorobenzene is reacted with 485 g of chloral. a. What mass of DDT is formed, assuming 100% yield? b. Which reactant is limiting? Which is in excess? c. What mass of the excess reactant is left over? d. If the actual yield of DDT is 200.0 g, what is the percent yield?

Hydrogen cyanide is produced industrially from the reaction of gaseous ammonia, oxygen, and methane: 2NH3(g) 1 3O2(g) 1 2CH4(g) 88n 2HCN(g) 1 6H2O(g) If 5.00 3 103 kg each of NH3, O2, and CH4 are reacted, what mass of HCN and of H2O will be produced, assuming 100% yield?

The production capacity for acrylonitrile (C3H3N) in the United States exceeds 2 million pounds per year. Acrylonitrile, the building block for polyacrylonitrile fibers and a variety of plastics, is produced from gaseous propylene, ammonia, and oxygen: 2C3H6(g) 1 2NH3(g) 1 3O2(g) 88n 2C3H3N(g) 1 6H2O(g) a. What mass of acrylonitrile can be produced from a mixture of 1.00 kg of propylene (C3H6), 1.50 kg of ammonia, and 2.00 kg of oxygen, assuming 100% yield? b. What mass of water is produced, and what masses of which starting materials are left in excess?

Consider the following unbalanced reaction: P4(s) 1 F2(g) 88n PF3(g) How many grams of F2 are needed to produce 120. g of PF3 if the reaction has a 78.1% yield?

The aspirin substitute acetaminophen (C8H9O2N) is produced by the following three-step synthesis: I. C6H5O3N(s) 1 3H2(g) 1 HCl(aq) 88n C6H8ONCl(s) 1 2H2O(l) II. C6H8ONCl(s) 1 NaOH(aq) 88n C6H7ON(s) 1 H2O(l) 1 NaCl(aq) III. C6H7ON(s) 1 C4H6O3(l) 88n C8H9O2N(s) 1 HC2H3O2(l) The first two reactions have percent yields of 87% and 98% by mass, respectively. The overall reaction yields 3 moles of acetaminophen product for every 4 moles of C6H5O3N reacted. a. What is the percent yield by mass for the overall process? b. What is the percent yield by mass of step III?

A given sample of a xenon fluoride compound contains molecules of the type XeFn, where n is some whole number. Given that 9.03 3 1020 molecules of XeFn weigh 0.368 g, determine the value for n in the formula.

Hemoglobin is the protein that transports oxygen in mammals. Hemoglobin is 0.347% Fe by mass, and each hemoglobin molecule contains four iron atoms. Calculate the molar mass of hemoglobin.

A sample of a hydrocarbon (a compound consisting of only carbon and hydrogen) contains 2.59 3 1023 atoms of hydrogen and is 17.3% hydrogen by mass. If the molar mass of the hydrocarbon is between 55 and 65 g/mol, how many moles of compound are present, and what is the mass of the sample?

A binary compound created by the reaction of an unknown element E and hydrogen contains 91.27% E and 8.73% H by mass. If the formula of the compound is E3H8, calculate the atomic mass of E.

An ionic compound MX3 is prepared according to the following unbalanced chemical equation: M 1 X2 88n MX3 A 0.105-g sample of X2 contains 8.92 3 1020 molecules. The compound MX3 consists of 54.47% X by mass. What are the identities of M and X, and what is the correct name for MX3? Starting with 1.00 g each of M and X2, what mass of MX3 can be prepared?

The empirical formula of styrene is CH; the molar mass of styrene is 104.14 g/mol. How many H atoms are present in a 2.00-g sample of styrene?

A 0.755-g sample of hydrated copper(II) sulfate (CuSO4 ? xH2O) was heated carefully until it had changed completely to anhydrous copper(II) sulfate (CuSO4) with a mass of 0.483 g. Determine the value of x. [This number is called the number of waters of hydration of copper(II) sulfate. It specifies the number of water molecules per formula unit of CuSO4 in the hydrated crystal.]

Many cereals are made with high moisture content so that the cereal can be formed into various shapes before it is dried. A cereal product containing 58% H2O by mass is produced at the rate of 1000. kg/h. How much water must be evaporated per hour if the final product contains only 20.% water?

When aluminum metal is heated with an element from Group 6A of the periodic table, an ionic compound forms. When the experiment is performed with an unknown Group 6A element, the product is 18.56% Al by mass. What is the formula of the compound?

A salt contains only barium and one of the halide ions. A 0.158-g sample of the salt was dissolved in water, and an excess of sulfuric acid was added to form barium sulfate (BaSO4), which was filtered, dried, and weighed. Its mass was found to be 0.124 g. What is the formula of the barium halide?

A sample of LSD (d-lysergic acid diethylamide, C24H30N3O) is added to some table salt (sodium chloride) to form a mixture. Given that a 1.00-g sample of the mixture undergoes combustion to produce 1.20 g of CO2, what is the mass percentage of LSD in the mixture?

Consider the following unbalanced equation: Ca3(PO4)2(s) 1 H2SO4(aq) 88n CaSO4(s) 1 H3PO4(aq) What masses of calcium sulfate and phosphoric acid can be produced from the reaction of 1.0 kg of calcium phosphate with 1.0 kg of concentrated sulfuric acid (98% H2SO4 by mass)?

A 0.4230-g sample of impure sodium nitrate was heated, converting all the sodium nitrate to 0.2864 g of sodium nitrite and oxygen gas. Determine the percent of sodium nitrate in the original sample.

You have seven closed containers, each with equal masses of chlorine gas (Cl2). You add 10.0 g of sodium to the first sample, 20.0 g of sodium to the second sample, and so on (adding 70.0 g of sodium to the seventh sample). Sodium and chlorine react to form sodium chloride according to the equation 2Na(s) 1 Cl2(g) 88n 2NaCl(s) After each reaction is complete, you collect and measure the amount of sodium chloride formed. A graph of your results is shown below. Mass of NaCl (g) Mass of Sodium (g) 0 4 20 0 60 80 Anwer the following questions: a. Explain the shape of the graph. b. Calculate the mass of NaCl formed when 20.0 g of sodium is used. c. Calculate the mass of Cl2 in each container. d. Calculate the mass of NaCl formed when 50.0 g of sodium is used. e. Identify the leftover reactant and determine its mass for parts b and d.

An iron ore sample contains Fe2O3 plus other impurities. A 752-g sample of impure iron ore is heated with excess carbon, producing 453 g of pure iron by the following reaction: Fe2O3(s) 1 3C(s) 88n 2Fe(s) 1 3CO(g) What is the mass percent of Fe2O3 in the impure iron ore sample? Assume that Fe2O3 is the only source of iron and that the reaction is 100% efficient

In using a mass spectrometer, a chemist sees a peak at a mass of 30.0106. Of the choices 12C2 1H6, 12C1H2 16O, and 14N16O, which is responsible for this peak? Pertinent masses are 1H, 1.007825; 16O, 15.994915; and 14N, 14.003074.

Natural rubidium has the average mass 85.4678 u and is composed of isotopes 85Rb (mass 5 84.9117 u) and 87Rb. The ratio of atoms 85Rb/87Rb in natural rubidium is 2.591. Calculate the mass of 87Rb.

Tetrodotoxin is a toxic chemical found in fugu pufferfish, a popular but rare delicacy in Japan. This compound has an LD50 (the amount of substance that is lethal to 50.% of a population sample) of 10. mg per kg of body mass. Tetrodotoxin is 41.38% carbon by mass, 13.16% nitrogen by mass, and 5.37% hydrogen by mass, with the remaining amount consisting of oxygen. What is the empirical formula of tetrodotoxin? If three molecules of tetrodotoxin have a mass of 1.59 3 10221 g, what is the molecular formula of tetrodotoxin? What number of molecules of tetrodotoxin would be the LD50 dosage for a person weighing 165 lb?

Consider the following data for three binary compounds of hydrogen and nitrogen: % H (by Mass) % N (by Mass) I 17.75 82.25 II 12.58 87.42 III 2.34 97.66 When 1.00 L of each gaseous compound is decomposed to its elements, the following volumes of H2(g) and N2(g) are obtained: H2 (L) N2 (L) I 1.50 0.50 II 2.00 1.00 III 0.50 1.50 Use these data to determine the molecular formulas of compounds I, II, and III and to determine the relative values for the atomic masses of hydrogen and nitrogen

A 0.200-g sample of protactinium(IV) oxide is converted to another oxide of protactinium by heating in the presence of oxygen to give 0.2081 g of the new oxide, PaxOy. Determine the values of x and y.

A 1.000-g sample of XI2 is dissolved in water, and excess silver nitrate is added to precipitate all of the iodide as AgI. The mass of the dry AgI is found to be 1.375 g. Calculate the atomic weight (mass) of X.

A substance X2Z has the composition (by mass) of 40.0% X and 60.0% Z. What is the composition (by mass) of the compound XZ2?

Vitamin A has a molar mass of 286.4 g and has a general molecular formula of CxHyE, where E is an unknown element. If vitamin A is 83.86% C and 10.56% H by mass, what is the molecular formula of vitamin A?

Boron consists of two isotopes, 10B and 11B. Chlorine also has two isotopes, 35Cl and 37Cl. Consider the mass spectrum of BCl3. How many peaks would be present, and what approximate mass would each peak correspond to in the BCl3 mass spectrum?

Consider samples of phosphine (PH3), water (H2O), hydrogen sulfide (H2S), and hydrogen fluoride (HF), each with a mass of 119 g. Rank the compounds from the least to the greatest number of hydrogen atoms contained in the samples.

Calculate the number of moles for each compound in the following table. Compound Mass Moles Magnesium phosphate 326.4 g _________ Calcium nitrate 303.0 g _________ Potassium chromate 141.6 g _________ Dinitrogen pentoxide 406.3 g _________

Arrange the following substances in order of increasing mass percent of nitrogen. a. NO c. NH3 b. N2O d. SNH

Para-cresol, a substance used as a disinfectant and in the manufacture of several herbicides, is a molecule that contains the elements carbon, hydrogen, and oxygen. Complete combustion of a 0.345-g sample of p-cresol produced 0.983 g carbon dioxide and 0.230 g water. Determine the empirical formula for p-cresol.

A compound with molar mass 180.1 g/mol has the following composition by mass: C 40.0% H 6.70% O 53.3% Determine the empirical and molecular formulas of the compound.

Which of the following statements about chemical equations is(are) true? a. When balancing a chemical equation, you can never change the coefficient in front of any chemical formula. b. The coefficients in a balanced chemical equation refer to the number of grams of reactants and products. c. In a chemical equation, the reactants are on the right and the products are on the left. d. When balancing a chemical equation, you can never change the subscripts of any chemical formula. e. In chemical reactions, matter is neither created nor destroyed so a chemical equation must have the same number of atoms on both sides of the equation

Consider the following unbalanced chemical equation for the combustion of pentane (C5H12): C5H12 1l2 1 O2 1g2 h CO2 1g2 1 H2O1l2 If 20.4 g of pentane are burned in excess oxygen, what mass of water can be produced, assuming 100% yield?

Sulfur dioxide gas reacts with sodium hydroxide to form sodium sulfite and water. The unbalanced chemical equation for this reaction is given below: SO2 1g2 1 NaOH1s2 h Na2SO3 1s2 1 H2O1l2 Assuming you react 38.3 g sulfur dioxide with 32.8 g sodium hydroxide and assuming that the reaction goes to completion, calculate the mass of each product formed.

In a mass spectrometer, positive ions are produced when a gaseous mixture is ionized by electron bombardment produced by an electric discharge. When the electricdischarge voltage is low, singly positive ions are produced and the following peaks are observed in the mass spectrum: Mass (u) Relative Intensity 32 0.3743 34 0.0015 40 1.0000 When the electric discharge is increased, still only singly charged ions are produced, but now the peaks observed in the mass spectrum are Mass (u) Relative Intensity 16 0.7500 18 0.0015 40 1.0000 What does the gas mixture consist of, and what is the percent composition by isotope of the mixture?

When the supply of oxygen is limited, iron metal reacts with oxygen to produce a mixture of FeO and Fe2O3. In a certain experiment, 20.00 g of iron metal was reacted with 11.20 g of oxygen gas. After the experiment, the iron was totally consumed and 3.24 g of oxygen gas remained. Calculate the amounts of FeO and Fe2O3 formed in this experiment.

Element X forms both a dichloride (XCl2) and a tetrachloride (XCl4). Treatment of 10.00 g of XCl2 with excess chlorine forms 12.55 g of XCl4. Calculate the atomic weight (mass) of X and identify X.

Zinc and magnesium metal each react with hydrochloric acid to make chloride salts of the respective metals and hydrogen gas. A 10.00-g mixture of zinc and magnesium produces 0.5171 g of hydrogen gas upon being mixed with an excess of hydrochloric acid. Determine the percent magnesium by mass in the original mixture.

An unknown binary compound containing hydrogen (XHn) has a density as a gas that is 2.393 times that of oxygen gas under the same conditions. When 2.23 3 1022 mole of this compound reacts with excess oxygen gas, 0.803 g of water is produced. Identify the element X in this compound.

A 2.25-g sample of scandium metal is reacted with excess hydrochloric acid to produce 0.1502 g hydrogen gas. What is the formula of the scandium chloride produced in the reaction?

When M2S3(s) is heated in air, it is converted to MO2(s). A 4.000-g sample of M2S3(s) shows a decrease in mass of 0.277 g when it is heated in air. What is the average atomic mass of M?

Consider a gaseous binary compound with a molar mass of 62.09 g/mol. When 1.39 g of this compound is completely burned in excess oxygen, 1.21 g of water is formed. Determine the formula of the compound.

Pure carbon was burned in an excess of oxygen. The gaseous products were CO2 72.0 mol% CO 16.0 mol% O2 12.0 mol% How many moles of O2 were present in the initial reaction mixture for every mole of carbon?

You take 1.00 g of an aspirin tablet (a compound consisting solely of carbon, hydrogen, and oxygen), burn it in air, and collect 2.20 g CO2 and 0.400 g H2O. You know that the molar mass of aspirin is between 170 and 190 g/mol. Reacting 1 mole of salicylic acid with 1 mole of acetic anhydride (C4H6O3) gives you 1 mole of aspirin and 1 mole of acetic acid (C2H4O2). Use this information to determine the molecular formula of salicylic acid.

Lanthanum was reacted with hydrogen in a given experiment to produce the nonstoichiometric compound LaH2.90. Assuming that the compound contains H2, La21, and La31, calculate the fraction of La21and La31 present

A 9.780-g gaseous mixture contains ethane (C2H6) and propane (C3H8). Complete combustion to form carbon dioxide and water requires 1.120 moles of oxygen gas. Calculate the mass percent of ethane in the original mixture

Consider a mixture of potassium chloride and potassium nitrate that is 43.2% potassium by mass. What is the percent KCl by mass of the original mixture?

An electric furnace produces phosphorus by the following reaction: Ca3(PO4)2(s) 1 5C(s) 1 3SiO2(s) 88n 3CaSiO3(s) 1 5CO(g) 1 2P(l) An initial reaction mixture contains 1500 kg calcium phosphate, 250 kg carbon, and 1.0 3 103 kg SiO2. a. What is the limiting reagent? b. What is the theoretical yield of phosphorus? c. After reaction the slag (solid residue) was analyzed. It contained 3.8% C, 5.8% P, and 26.6% Ca by mass. What was the actual yield of phosphorus in kg? What was the percent yield?

Ammonia reacts with O2 to form either NO(g) or NO2(g) according to these unbalanced equations: NH3(g) 1 O2(g) 88n NO(g) 1 H2O(g) NH3(g) 1 O2(g) 88n NO2(g) 1 H2O(g) In a certain experiment, 2.00 moles of NH3(g) and 10.00 moles of O2(g) are contained in a closed flask. After the reaction is complete, 6.75 moles of O2(g) remains. Calculate the number of moles of NO(g) in the product mixture. (Hint: You cannot do this problem by adding the balanced equations because you cannot assume that the two reactions will occur with equal probability.)

A gas contains a mixture of NH3(g) and N2H4(g), both of which react with O2(g) to form NO2(g) and H2O(g). The gaseous mixture (with an initial mass of 61.00 g) is reacted with 10.00 moles O2, and after the reaction is complete, 4.062 moles of O2 remains. Calculate the mass percent of N2H4(g) in the original gaseous mixture.

A 2.077-g sample of an element, which has an atomic mass between 40 and 55, reacts with oxygen to form 3.708 g of an oxide. Determine the formula of the oxide and identify the element.

Consider the following balanced chemical equation: A 1 5B 88n 3C 1 4D a. Equal masses of A and B are reacted. Complete each of the following with either A is the limiting reactant because _____; B is the limiting reactant because _____; or We cannot determine the limiting reactant because _____. i. If the molar mass of A is greater than the molar mass of B, then ii. If the molar mass of B is greater than the molar mass of A, then b. The products of the reaction are carbon dioxide (C) and water (D). Compound A has a similar molar mass to carbon dioxide. Compound B is a diatomic molecule. Identify compound B and support your answer. c. Compound A is a hydrocarbon that is 81.71% carbon by mass. Determine its empirical and molecular formulas.