### Problem 124

Fructose is a common sugar found in fruit. Elemental analysis of fructose gives the following mass percent composition: C 40.00%, H 6.72%, O 53.28%. The molar mass of fructose is 180.16 g>mol. Find the molecular formula of fructose.

### Problem 125

Combustion analysis of a 13.42-g sample of equilin (which contains only carbon, hydrogen, and oxygen) produces 39.61 g CO2 and 9.01 g H2O. The molar mass of equilin is 268.34 g>mol. Find its molecular formula.

### Problem 126

Estrone, which contains only carbon, hydrogen, and oxygen, is a female sexual hormone that occurs in the urine of pregnant women. Combustion analysis of a 1.893-g sample of estrone produces 5.545 g of CO2 and 1.388 g H2O. The molar mass of estrone is 270.36 g>mol. Find its molecular formula.

### Problem 127

Epsom salts is a hydrated ionic compound with the following formula: MgSO4 # x H2O. A 4.93-g sample of Epsom salts was heated to drive off the water of hydration. The mass of the sample after complete dehydration was 2.41 g. Find the number of waters of hydration (x) in Epsom salts

### Problem 128

A hydrate of copper(II) chloride has the following formula: CuCl2 # x H2O. The water in a 3.41-g sample of the hydrate is driven off by heating. The remaining sample has a mass of 2.69 g. Find the number of waters of hydration (x) in the hydrate.

### Problem 129

A compound of molar mass 177 g>mol contains only carbon, hydrogen, bromine, and oxygen. Analysis reveals that the compound contains 8 times as much carbon as hydrogen by mass. Find the molecular formula.

Charotte M.

### Problem 130

Researchers obtain the following data from experiments to find the molecular formula of benzocaine, a local anesthetic, which contains only carbon, hydrogen, nitrogen, and oxygen. Complete combustion of a 3.54-g sample of benzocaine with excess O2 forms 8.49 g of CO2 and 2.14 g H2O. Another sample of mass 2.35 g is found to contain 0.199 g of N. The molar mass of benzocaine is found to be 165 g>mol. Find the molecular formula of benzocaine.

### Problem 131

Find the total number of atoms in a sample of cocaine hydrochloride, C17H22CINO4, of mass 23.5 mg.

### Problem 132

Vanadium forms four different oxides in which the percent by mass of vanadium is, respectively, (a) 76%, (b) 68%, (c) 61%, and (d) 56%. Determine the formula and the name of each one of these oxides.

### Problem 133

The chloride of an unknown metal is believed to have the formula MCl3. A 2.395-g sample of the compound contains 3.606 * 10-2 mol Cl. Find the atomic mass of M.

Charotte M.

### Problem 134

Write the structural formulas of two different compounds that each has the molecular formula C4H10.

Jessica L.
Florida International University

### Problem 135

A chromium-containing compound has the formula FexCryO4 and is 28.59% oxygen by mass. Find x and y.

Charotte M.

### Problem 136

A phosphorus compound that contains 34.00% phosphorus by mass has the formula X3P2. Identify the element X.

### Problem 137

A particular brand of beef jerky contains 0.0552% sodium nitrite by mass and is sold in an 8.00-oz bag. What mass of sodium does the sodium nitrite contribute to the sodium content of the bag of beef jerky?

### Problem 138

Phosphorus is obtained primarily from ores containing calcium phosphate. If a particular ore contains 57.8% calcium phosphate, what minimum mass of the ore must be processed to obtain 1.00 kg of phosphorus?

### Problem 139

A mixture of NaCl and NaBr has a mass of 2.00 g and contains 0.75 g of Na. What is the mass of NaBr in the mixture?

### Problem 140

Three pure compounds form when 1.00-g samples of element X combine with, respectively, 0.472 g, 0.630 g, and 0.789 g of element Z. The first compound has the formula X2Z3. Find the empirical formulas of the other two compounds.

### Problem 141

A mixture of CaCO3 and (NH4)2CO3 is 61.9% CO3 by mass. Find the mass percent of CaCO3 in the mixture.

Charotte M.

### Problem 142

A mixture of 50.0 g of S and 1.00 * 102 g of Cl2 reacts completely to form S2Cl2 and SCl2. What mass of S2Cl2 forms?

### Problem 143

Because of increasing evidence of damage to the ozone layer, chlorofluorocarbon (CFC) production was banned in 1996. However, there are about 100 million auto air conditioners in operation that still use CFC-12 (CF2Cl2). These air conditioners are recharged from stockpiled supplies of CFC-12. If each of the 100 million automobiles contains 1.1 kg of CFC-12 and leaks 25% of its CFC-12 into the atmosphere per year, how much chlorine, in kg, is added to the atmosphere each year due to auto air conditioners? (Assume two significant figures in your calculations.)

### Problem 144

A particular coal contains 2.55% sulfur by mass. When the coal is burned, it produces SO2 emissions, which combine with rainwater to produce sulfuric acid. Use the formula of sulfuric acid to calculate the mass percent of S in sulfuric acid. Then determine how much sulfuric acid (in metric tons) is produced by the combustion of 1.0 metric ton of this coal. (A metric ton is 1000 kg.)

Charotte M.

### Problem 145

Lead is found in Earth's crust as several different lead ores. Suppose a certain rock is 38.0% PbS (galena), 25.0% PbCO3 (cerussite), and 17.4% PbSO4 (anglesite). The remainder of the rock is composed of substances containing no lead. How much of this rock (in kg) must be processed to obtain 5.0 metric tons of lead? (A metric ton is 1000 kg.)

David C.

### Problem 146

A 2.52-g sample of a compound containing only carbon, hydrogen, nitrogen, oxygen, and sulfur is burned in excess oxygen to yield 4.23 g of CO2 and 1.01 g of H2O. Another sample of the same compound, of mass 4.14 g, yields 2.11 g of SO3. A third sample, of mass 5.66 g, yields 2.27 g of HNO3. Calculate the
empirical formula of the compound. (Hint: Use the first set of data to determine % C and % H by mass. Use the second and third sets of data to determine % S and % N by mass. Then determine % O by mass by difference from 100%.)

David C.

### Problem 147

A compound of molar mass 229 contains only carbon, hydrogen, iodine, and sulfur. Analysis shows that a sample of the compound contains 6 times as much carbon as hydrogen, by mass. Calculate the molecular formula of the compound.

### Problem 148

The elements X and Y form a compound that is 40% X and 60% Y by mass. The atomic mass of X is twice that of Y. What is the empirical formula of the compound?

### Problem 149

A compound of X and Y is 13 X by mass. The atomic mass of element X is one-third the atomic mass of element Y. Find the empirical formula of the compound.

### Problem 150

A mixture of carbon and sulfur has a mass of 9.0 g. Complete combustion with excess O2 gives 23.3 g of a mixture of CO2 and SO2. Find the mass of sulfur in the original mixture.

### Problem 151

When molecules are represented by molecular models, what does each sphere represent? How big is the nucleus of an atom in comparison to the sphere used to represent an atom in a molecular model?

### Problem 152

Without doing any calculations, determine which element in each of the compounds will have the highest mass percent composition.
a. CO
b. N2O
c. C6H12O6
d. NH3

Jessica L.
Florida International University

### Problem 153

Explain the problem with this statement and correct it: "The chemical formula for ammonia (NH3) indicates that ammonia contains 3 grams of hydrogen to each gram of nitrogen."

### Problem 154

Without doing any calculations, arrange the elements in H2SO4 in order of decreasing mass percent composition.

Jessica L.
Florida International University

### Problem 155

Using group members to play the roles of nuclei and electrons, demonstrate the formation of an ionic bond between Na and Cl. Demonstrate the formation of the covalent bonds in H2O.

Thomas W.

### Problem 156

Create a flowchart with a series of simple questions that can be used to determine whether a chemical formula is that of an atomic element, a molecular element, a molecular compound, or an ionic compound. Use your flowchart to identify the correct category for P4, KCl, CH4, Ne, and NH4NO3.

### Problem 157

Have each member of your group list one similarity or difference between the naming conventions for ionic and the naming conventions of molecular compounds.

Thomas W.

### Problem 158

A compound isolated from the rind of lemons is 88.14% carbon and 11.86% hydrogen by mass. How many grams of C and H are there in a 100.0-g sample of this substance? How many moles of C and H? What is the empirical formula? The molar mass is determined to be 136.26 g>mol. What is the molecular formula? Which step of the process just described does your group understand the least? Which step will be most challenging for the members of your group to remember?

Thomas W.

### Problem 159

The amount of carbon dioxide in the atmosphere has been increasing over the past century as a result of the combustion of fossil fuels (coal, oil, and natural gas). Carbon dioxide is a greenhouse gas that plays a significant role in climate. The increase in carbon dioxide is correlated with changes in climate that have climate scientists concerned. The graph shown here illustrates the increase in atmospheric carbon dioxide from 1860 to the present. Study the graph and answer the questions that follow.

Atmospheric carbon dioxide concentration from 1850 to present.

a. By how much did the level of carbon dioxide (in ppmv) increase between 1880 and the present day?
b. What is the percent increase in the level of carbon dioxide between 1880 and the present day?
c. Assuming that the total volume of air in the atmosphere around Earth is 5.1 * 109 km3 and that the concentration of CO2 is uniform throught this volume, what is the present-day volume of CO2 in the atmosphere?
d. Determine the percentage average yearly increase in atmospheric CO2 from 1960 to the present day.
e. If atmospheric carbon dioxide continues to increase at the rate you determined in part d, what will its concentration (in ppmv) be in the year 2040?

Thomas W.