Gallium arsenide, GaAs, has gained widespread use in

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 youll make. e. A mole-to-mole ratio must be established for the reaction to occur as written. Justify the best choice, and for choices you did not pick, explain what is wrong with them.

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

You are making cookies and are missing a key ingredienteggs. You have most of the other ingredients needed to make the cookies, except you have only 1.33 cups of butter and no eggs. You note that the recipe calls for 2 cups of butter and 3 eggs (plus the other ingredients) to make 6 dozen cookies. You call a friend and have him bring you some eggs. a. What number of eggs do you need? b. If you use all the butter (and get enough eggs), what number of cookies will you make? Unfortunately, your friend hangs up before you tell him how many eggs you need. When he arrives, he has a surprise for you to save time, he has broken them all in a bowl for you. You ask him how many he brought, and he replies, I cant remember. You weigh the eggs and find that they weigh 62.1 g. Assuming that an average egg weighs 34.21 g, a. What quantity of butter is needed to react with all the eggs? b. What number of cookies can you make? c. Which will you have left over, eggs or butter? d. What quantity is 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 below

For the preceding question, which of the following equations best represents the reaction? a. b. c. d. e. Justify your choice, and for choices you did not pick, explain what is wrong with them

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 determine the amount of product that will be produced? Explain.

A new grill has a mass of 30.0 kg. You put 3.0 kg of charcoal in the grill. You burn all the charcoal and the grill has a mass of 30.0 kg. What is the mass of the gases given off? Explain.

Consider an iron bar on a balance as shown.

You may have noticed that water sometimes drips from the exhaust 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 10 g b. between 20 and 100 g c. between 100 and 120 g d. exactly 120 g e. more than 120 g

What is true about the chemical properties of the product? a. The properties are more like chemical A. b. The properties are more like chemical B. c. The properties are an average of those of chemical A and chemical B. d. The properties are not necessarily like either chemical A or chemical B. e. The properties are more like chemical A or more like chemical B, but more information is needed. Justify your choice, and for choices you did not pick, explain what is wrong with them

Is there a difference between a homogeneous mixture of hydrogen and oxygen in a 2:1 mole ratio and a sample of water vapor? Explain.

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

The average mass of a carbon atom is 12.011. Assuming you could pick up one carbon atom, estimate the chance that you would randomly get one with a mass of 12.011. Support your answer.

Can the subscripts in a chemical formula be fractions? Explain. Can the coefficients in a balanced chemical equation be fractions? Explain. Changing the subscripts of chemicals can balance the equations mathematically. Why is this unacceptable?

Consider the equation If you mix 1.0 mol of A with 1.0 mol of B, what amount (moles) of A2B can be produced?

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?

Which of the following pairs of compounds have the same empirical formula? a. acetylene, C2H2, and benzene, C6H6 b. ethane, C2H6, and butane, C4H10 c. nitrogen dioxide, NO2, and dinitrogen tetroxide, N2O4 d. diphenyl ether, C12H10O, and phenol, C6H5OH

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

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 . 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.

Reference Section 3.2 to find the atomic masses of 12C and 13C, the relative abundance of 12C and 13C in natural carbon, and the average mass (in amu) of a carbon atom. If you had a sample of natural carbon containing exactly 10,000 atoms, determine the number of 12C and 13C atoms present. What would be the average mass (in amu) and the total mass (in amu) of the carbon atoms in this 10,000-atom sample? If you had a sample of natural carbon containing 6.0221  1023 atoms, determine the number of 12C and 13C atoms present. What would be the average mass (in amu) and the total mass (in amu) of this 6.0221  1023 atom sample? Given that 1 g  6.0221  1023 amu, what is the total mass of 1 mol of natural carbon in units of grams?

Avogadros number, molar mass, and the chemical formula of a compound are three useful conversion factors. What unit conversions can be accomplished using these conversion factors?

If you had a mol of U.S. dollar bills and equally distributed the money to all of the people of the world, how rich would every person be? Assume a world population of 6 billion.

What is the difference between the molar mass and the empirical formula mass of a compound? When are these masses the same and when are they different? When different, how is the molar mass related to the empirical formula mass?

How is the mass percent of elements in a compound different for a 1.0-g sample versus a 100.-g sample versus a 1-mol sample of the compound?

A balanced chemical equation contains a large amount of information. What information is given in a balanced equation?

What is the theoretical yield for a reaction, and how does this quantity depend on the limiting reactant?

What does it mean to say a reactant is present in excess in a process? Can the limiting reactant be present in excess? Does the presence of an excess of a reactant affect the mass of products expected for a reaction?

Consider the following generic reaction: What steps and information are necessary to perform the following determinations assuming that 1.00  104 molecules of A2B2 are reacted with excess C? a. mass of CB produced b. atoms of A produced c. mol of C reacted d. percent yield of CB

Consider the following generic reaction: In a limiting reactant problem, a certain quantity of each reactant is given and you are usually asked to calculate the mass of product formed. If 10.0 g of Y2 is reacted with 10.0 g of XY, outline two methods you could use to determine which reactant is limiting (runs out first) and thus determines the mass of product formed. A method sometimes used to solve limiting reactant problems is to assume each reactant is limiting and then calculate the mass of product formed from each given quantity of reactant. How does this method work in determining which reactant is limiting?

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

An element X has five major isotopes, which are listed below along with their abundances. What is the element?

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

Assume silicon has three major isotopes in nature as shown in the table below. Fill in the missing information

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

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

The mass spectrum of bromine (Br2) consists of three peaks with the following characteristics: Mass (amu) Relative Size 157.84 0.2534 159.84 0.5000 161.84 0.2466 How do you interpret these data?

Gallium arsenide, GaAs, has gained widespread use in semiconductor devices that convert light and electrical signals in fiberoptic 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 the formulas GaAs and Ga2As2. What would the distribution of peaks look like for these two fragments?

Calculate the mass of 500. atoms of iron (Fe)

What number of Fe atoms and what amount (moles) of Fe atoms are in 500.0 g of iron?

Diamond is a natural form of pure carbon. What number of atoms of carbon are in a 1.00-carat diamond (1.00 carat  0.200 g)?

A diamond contains 5.0  1021 atoms of carbon. What amount (moles) of carbon and what mass (grams) of carbon are in this diamond?

Aluminum metal is produced by passing an electric current through a solution of aluminum oxide (Al2O3) dissolved in molten cryolite (Na3AlF6). Calculate the molar masses of Al2O3 and Na3AlF6.

The Freons are a class of compounds containing carbon, chlorine, and fluorine. While they have many valuable uses, they have been shown to be responsible for depletion of the ozone in the upper atmosphere. In 1991, two replacement compounds for Freons went into production: HFC-134a (CH2FCF3) and HCFC-124 (CHClFCF3). Calculate the molar masses of these two compounds.

Calculate the molar mass of the following substances. a. b. c. (NH4)2Cr2O7

Calculate the molar mass of the following substances. a. b. Ca3(PO4)2 c. Na2HPO4

What amount (moles) of compound is present in 1.00 g of each of the compounds in Exercise 47?

What amount (moles) of compound is present in 1.00 g of each of the compounds in Exercise 48?

What mass of compound is present in 5.00 mol of each of the compounds in Exercise 47?

What mass of compound is present in 5.00 mol of each of the compounds in Exercise 48?

What mass of nitrogen is present in 5.00 mol of each of the compounds in Exercise 47?

What mass of phosphorus is present in 5.00 mol of each of the compounds in Exercise 48?

What number of molecules (or formula units) are present in 1.00 g of each of the compounds in Exercise 47?

What number of molecules (or formula units) are present in 1.00 g of each of the compounds in Exercise 48?

What number of atoms of nitrogen are present in 1.00 g of each of the compounds in Exercise 47?

What number of atoms of phosphorus are present in 1.00 g of each of the compounds in Exercise 48?

Freon-12 (CCl2F2) is used as a refrigerant in air conditioners and as a propellant in aerosol cans. Calculate the number of molecules of Freon-12 in 5.56 mg of Freon-12. What is the mass of chlorine in 5.56 mg of Freon-12?

Bauxite, the principal ore used in the production of aluminum, has a molecular formula of Al2O3 2H2O. a. What is the molar mass of bauxite? b. What is the mass of aluminum in 0.58 mol bauxite? c. How many atoms of aluminum are in 0.58 mol bauxite? d. What is the mass of 2.1  1024 formula units of bauxite?

What amount (moles) is represented by each of these samples? a. 150.0 g Fe2O3 b. 10.0 mg NO2 c. 1.5  1016 molecules of BF3

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

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

Complete the following table.

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. What amount (moles) of C2H3Cl3O2 molecules are in 500.0 g chloral hydrate? c. What is the mass in grams of 2.0  102 mol chloral hydrate? d. What number of 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 of exactly 500 molecules of chloral hydrate?

Dimethylnitrosamine, (CH3)2N2O, is a carcinogenic (cancercausing) substance that may be formed in foods, beverages, or gastric juices from the reaction of nitrite ion (used as a food preservative) with other substances. a. What is the molar mass of dimethylnitrosamine? b. How many moles of (CH3)2N2O molecules are present in 250 mg dimethylnitrosamine? c. What is the mass of 0.050 mol dimethylnitrosamine? d. How many atoms of hydrogen are in 1.0 mol dimethylnitrosamine? e. What is the mass of 1.0  106 molecules of dimethylnitrosamine? f. What is the mass in grams of one molecule of dimethylnitrosamine?

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.

Several important compounds contain only nitrogen and oxygen. Place the following compounds in order of increasing mass percent of nitrogen. a. NO, a gas formed by the reaction of N2 with O2 in internal combustion engines b. NO2, a brown gas mainly responsible for the brownish color of photochemical smog c. N2O4, a colorless liquid used as fuel in space shuttles d. N2O, a colorless gas sometimes used as an anesthetic by dentists (known as laughing gas)

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

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?

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.

Express the composition of each of the following compounds as the mass percents of its elements. a. formaldehyde, CH2O b. glucose, C6H12O6 c. acetic acid, HC2H3O2

Considering your answer to Exercise 73, which type of formula, empirical or molecular, can be obtained from elemental analysis that gives percent composition?

Give the empirical formula for each of the compounds represented below. 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 compound that contains only carbon, hydrogen, and oxygen is 48.64% C and 8.16% H by mass. What is the empirical formula of this substance?

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

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.

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?

A compound containing only sulfur and nitrogen is 69.6% S by mass; the molar mass is 184 g/mol. What are the empirical and molecular formulas of the compound?

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.

A compound contains 47.08% carbon, 6.59% hydrogen, and 46.33% chlorine by mass; the molar mass of the compound is 153 g/mol. What are the empirical and molecular formulas of the compound?

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

Many homes in rural America are heated by propane gas, a compound that contains only carbon and hydrogen. Complete combustion of a sample of propane produced 2.641 g of carbon dioxide and 1.442 g of water as the only products. Find the empirical formula of propane

A compound contains only C, H, and N. Combustion of 35.0 mg of the compound produces 33.5 mg CO2 and 41.1 mg H2O. What is the empirical formula of the compound?

Cumene is a compound containing only carbon and hydrogen that is used in the production of acetone and phenol in the chemical industry. Combustion of 47.6 mg cumene produces some CO2 and 42.8 mg water. The molar mass of cumene is between 115 and 125 g/mol. Determine the empirical and molecular formulas

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?

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).

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. c. Solid zinc reacts with aqueous HCl to form aqueous zinc chloride and hydrogen gas. d. Aqueous strontium hydroxide reacts with aqueous hydrobromic acid to produce water and aqueous strontium bromide

A common demonstration in chemistry courses involves adding a tiny speck of manganese(IV) oxide to a concentrated hydrogen peroxide (H2O2) solution. Hydrogen peroxide decomposes quite spectacularly under these conditions to produce oxygen gas and steam (water vapor). Manganese(IV) oxide is a catalyst for the decomposition of hydrogen peroxide and is not consumed in the reaction. Write the balanced equation for the decomposition reaction of hydrogen peroxide.

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:

Balance the following equations:

Balance each of the following chemical equations

Balance the following equations representing combustion reactions: a. b. (g) ( + + g) (g) (g) (l) ( + + (g) g) (g) H O

Balance the following equations:

Silicon is produced for the chemical and electronics industries by the following reactions. Give the balanced equation for each reaction. a. b. Silicon tetrachloride is reacted with very pure magnesium, producing silicon and magnesium chloride.

Glass is a mixture of several compounds, but a major constituent of most glass is calcium silicate, CaSiO3. Glass can be etched by treatment with hydrofluoric acid; HF attacks the calcium silicate of the glass, producing gaseous and water-soluble products (which can be removed by washing the glass). For example, the volumetric glassware in chemistry laboratories is often graduated by using this process. Balance the following equation for the reaction of hydrofluoric acid with calcium silicate.

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 What masses of iron(III) oxide and aluminum must be used to produce 15.0 g 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 decaoxide (P4O10) would be produced?

The reusable booster rockets of the U.S. space shuttle employ a mixture of aluminum and ammonium perchlorate for fuel. A possible equation for this reaction is 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 Ba1SCN221s2  H2O1l2  NH31g2 Ba1OH22  8H2O1s2  NH4SCN1s2

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

Phosphorus can be prepared from calcium phosphate by the following reaction: Phosphorite is a mineral that contains Ca3(PO4)2 plus other nonphosphorus-containing compounds. What is the maximum amount of P4 that can be produced from 1.0 kg of phosphorite if the phorphorite sample is 75% Ca3(PO4)2 by mass? Assume an excess of the other reactants.

Coke is an impure form of carbon that is often used in the industrial production of metals from their oxides. If a sample of coke is 95% carbon by mass, determine the mass of coke needed to react completely with 1.0 ton of copper(II) oxide

The space shuttle environmental control system handles 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 are 7 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.

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

Consider the following reaction: 4NH31g2  5O21g2 4NO1g2  6H2O1g2 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?

Ammonia is produced from the reaction of nitrogen and hydrogen according to the following balanced equation: a. What is the maximum mass of ammonia that can be produced from a mixture of 1.00  103 g N2 and 5.00  102 g H2? b. What mass of which starting material would remain unreacted?

Consider the following unbalanced equation: What masses of calcium sulfate and phosphoric acid can be produced from the reaction of 1.0 kg calcium phosphate with 1.0 kg concentrated sulfuric acid (98% H2SO4 by mass)?

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

Acrylonitrile (C3H3N) is the starting material for many synthetic carpets and fabrics. It is produced by the following reaction. If 15.0 g C3H6, 10.0 g O2, and 5.00 g NH3 are reacted, what mass of acrylonitrile can be produced, assuming 100% yield?

The reaction of ethane gas (C2H6) with chlorine gas produces C2H5Cl as its main product (along with HCl). In addition, the reaction invariably produces a variety of other minor products, including C2H4Cl2, C2H3Cl3, and others. Naturally, the production of these minor products reduces the yield of the main product. Calculate the percent yield of C2H5Cl if the reaction of 300. g of ethane with 650. g of chlorine produced 490. g of C2H5Cl.

DDT, an insecticide harmful to fish, birds, and humans, is produced by the following reaction: 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? 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?

Bornite (Cu3FeS3) is a copper ore used in the production of copper. When heated, the following reaction occurs: If 2.50 metric tons of bornite is reacted with excess O2 and the process has an 86.3% yield of copper, what mass of copper is produced?

Consider the following unbalanced reaction: What mass of F2 is needed to produce 120. g of PF3 if the reaction has a 78.1% yield?

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) and what number of molecules of vitamin C does it contain?

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?

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

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.

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.

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

Adipic acid is an organic compound composed of 49.31% C, 43.79% O, and the rest hydrogen. If the molar mass of adipic acid is 146.1 g/mol, what are the empirical and molecular formulas for adipic acid?

Bacterial digestion is an economical method of sewage treatment. The reaction bacterial tissue C5H7O2N1s2  54NO2  1aq2  52H2O1l2  109H 1aq2 5CO21g2  55NH4  1aq2  76O21g2 bacteria is an intermediate step in the conversion of the nitrogen in organic compounds into nitrate ions. What mass of bacterial tissue is produced in a treatment plant for every 1.0  104 kg of wastewater containing 3.0% NH4  ions by mass? Assume that 95% of the ammonium ions are consumed by the bacteria

Aspirin (C9H8O4) is synthesized by reacting salicylic acid (C7H6O3) with acetic anhydride (C4H6O3). The balanced equation is a. What mass of acetic anhydride is needed to completely consume 1.00  102 g salicylic acid? b. What is the maximum mass of aspirin (the theoretical yield) that could be produced in this reaction?

A student prepared aspirin in a laboratory experiment using the reaction in Exercise 125. The student reacted 1.50 g salicylic acid with 2.00 g acetic anhydride. The yield was 1.50 g aspirin. Calculate the theoretical yield and the percent yield for this experiment.

Hydrogen peroxide is used as a cleansing agent in the treatment of cuts and abrasions for several reasons. It is an oxidizing agent that can directly kill many microorganisms; it decomposes on contact with blood, releasing elemental oxygen gas (which inhibits the growth of anaerobic microorganisms); and it foams on 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: What mass of hydrogen peroxide should result when 1.50 g barium peroxide is treated with 25.0 mL hydrochloric acid solution containing 0.0272 g 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 Ag2O is reacted with 50.0 g C10H10N4SO2, what mass of silver sulfadiazine, AgC10H9N4SO2, can be produced, assuming 100% yield?

In using a mass spectrometer, a chemist sees a peak at a mass of 30.0106. Of the choices 12C2 1 H6, 12C1 H2 16O, and 14N16O, which is responsible for this peak? Pertinent masses are 1 H, 1.007825; 16O, 15.994915; and 14N, 14.003074

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?

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

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. What mass of water must be evaporated per hour if the final product contains only 20.% water?

Consider the reaction Identify the limiting reagent in each of the reaction mixtures given below: a. 50 molecules of H2 and 25 molecules of O2 b. 100 molecules of H2 and 40 molecules of O2 c. 100 molecules of H2 and 100 molecules of O2 d. 0.50 mol H2 and 0.75 mol O2 e. 0.80 mol H2 and 0.75 mol O2 f. 1.0 g H2 and 0.25 mol O2 g. 5.00 g H2 and 56.00 g O2

Some bismuth tablets, a medication used to treat upset stomachs, contain 262 mg of bismuth subsalicylate, C7H5BiO4, per tablet. Assuming two tablets are digested, calculate the mass of bismuth consumed

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

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 mol of terephthalic acid has a mass of 41.5 g, determine the molecular formula for terephthalic acid

A sample of a hydrocarbon (a compound consisting of only carbon and hydrogen) contains 2.59  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, what amount (moles) of compound is present, and what is the mass of the sample?

A binary compound between 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.

A 0.755-g sample of hydrated copper(II) sulfate 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.]

ABS plastic is a tough, hard plastic used in applications requiring shock resistance. 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?

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 percent of LSD in the mixture?

Methane (CH4) is the main component of marsh gas. Heating methane in the presence of sulfur produces carbon disulfide and hydrogen sulfide as the only products. a. Write the balanced chemical equation for the reaction of methane and sulfur. b. Calculate the theoretical yield of carbon disulfide when 120. g of methane is reacted with an equal mass of sulfur

A potential fuel for rockets is a combination of B5H9 and O2. The two react according to the following balanced equation: If one tank in a rocket holds 126 g B5H9 and another tank holds 192 g O2, what mass of water can be produced when the entire contents of each tank react together?

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.

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: 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

Commercial brass, an alloy of Zn and Cu, reacts with hydrochloric acid as follows: (Cu does not react with HCl.) When 0.5065 g of a certain brass alloy is reacted with excess HCl, 0.0985 g ZnCl2 is eventually isolated. a. What is the composition of the brass by mass? b. How could this result be checked without changing the above procedure?

Vitamin A has a molar mass of 286.4 g/mol and 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?

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?

Consider the following data for three binary compounds of hydrogen and nitrogen: When 1.00 L of each gaseous compound is decomposed to its elements, the following volumes of H2(g) and N2(g) are obtained: % H (by Mass) % N (by Mass) I 17.75 82.25 II 12.58 87.42 III 2.34 97.66 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

Natural rubidium has the average mass of 85.4678 and is composed of isotopes 85Rb (mass  84.9117) and 87Rb. The ratio of atoms 85Rb87Rb in natural rubidium is 2.591. Calculate the mass of 87Rb.

A compound contains only carbon, hydrogen, nitrogen, and oxygen. Combustion of 0.157 g of the compound produced 0.213 g CO2 and 0.0310 g H2O. In another experiment, it is found that 0.103 g of the compound produces 0.0230 g 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.

Nitric acid is produced commercially by the Ostwald process, represented by the following equations: What mass of NH3 must be used to produce 1.0  106 kg HNO3 by the Ostwald process? Assume 100% yield in each reaction and assume that the NO produced in the third step is not recycled.

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 iron metal was reacted with 11.20 g oxygen gas. After the experiment, the iron was totally consumed, and 3.24 g oxygen gas remained. Calculate the amounts of FeO and Fe2O3 formed in this experiment.

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

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

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 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. Assume water is the only product that contains hydrogen

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?

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 A plant needs to manufacture 10,000 printed circuit boards, each 8.0  16.0 cm in area. An average of 80.% of the copper is removed from each board (density of copper  8.96 g/cm3 ). What masses of Cu(NH3)4Cl2 and NH3 are needed to do this? Assume 100% yield.

The aspirin substitute, acetaminophen (C8H9O2N), is produced by the following three-step synthesis: I. II. III. The first two reactions have percent yields of 87% and 98% by mass, respectively. The overall reaction yields 3 mol of acetaminophen product for every 4 mol 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?

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

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?

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?

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?

Ammonia reacts with O2 to form either NO(g) or NO2(g) according to these unbalanced equations: In a certain experiment 2.00 mol NH3(g) and 10.00 mol O2(g) are contained in a closed flask. After the reaction is complete, 6.75 mol 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.)

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.

With the advent of techniques such as scanning tunneling microscopy, it is now possible to write with individual atoms by manipulating and arranging atoms on an atomic surface. a. If an image is prepared by manipulating iron atoms and their total mass is 1.05  1020 g, what number of iron atoms were used? b. If the image is prepared on a platinum surface that is exactly 20 platinum atoms high and 14 platinum atoms wide, what is the mass (grams) of the atomic surface? c. If the atomic surface were changed to ruthenium atoms and the same surface mass as determined in part b is used, what number of ruthenium atoms is needed to construct the surface?

Tetrodotoxin is a toxic chemical found in fugu pufferfish, a popular but rare delicacy in Japan. This compound has a LD50 (the amount of substance that is lethal to 50.% of a population sample) of 10. g 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  1021 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?

An ionic compound MX3 is prepared according to the following unbalanced chemical equation. A 0.105-g sample of X2 contains 8.92  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 compound As2I4 is synthesized by reaction of arsenic metal with arsenic triiodide. If a solid cubic block of arsenic (d  5.72 g/cm3 ) that is 3.00 cm on edge is allowed to react with 1.01  1024 molecules of arsenic triiodide, what mass of As2I4 can be prepared? If the percent yield of As2I4 was 75.6%, what mass of As2I4 was actually isolated

From the information below, determine the mass of substance C that will be formed if 45.0 grams of substance A reacts with 23.0 grams of substance B. (Assume that the reaction between A and B goes to completion.) a. Substance A is a gray solid that consists of an alkaline earth metal and carbon (37.5% by mass). It reacts with substance B to produce substances C and D. Forty million trillion formula units of A have a mass of 4.26 milligrams. b. 47.9 grams of substance B contains 5.36 grams of hydrogen and 42.5 grams of oxygen. c. When 10.0 grams of C is burned in excess oxygen, 33.8 grams of carbon dioxide and 6.92 grams of water are produced. A mass spectrum of substance C shows a parent molecular ion with a mass-to-charge ratio of 26. d. Substance D is the hydroxide of the metal in substance A.

Consider the following balanced chemical equation: 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 the same molar mass as 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.