Chapter 3

Copper(II) fluoride contains \(37.42 \%\) F by mass. Calculate the mass of fluorine (in g) in \(55.5 \mathrm{~g}\) of copper(II) fluoride.

The iodide ion is a dietary mineral essential to good nutrition. In countries where potassium iodide is added to salt, iodine deficiency (or goiter) has been almost completely eliminated. The recommended daily allowance (RDA) for iodine is \(150 \mu \mathrm{g} /\) day. How much potassium iodide (76.45\% I) should you consume if you want to meet the RDA?

The American Dental Association recommends that an adult female should consume \(3.0 \mathrm{mg}\) of fluoride \(\left(\mathrm{F}^{-}\right)\) per day to prevent tooth decay. If the fluoride is consumed in the form of sodium fluoride \((45.24 \% \mathrm{~F}),\) what amount of sodium fluoride contains the recommended amount of fluoride?

Determine the number of moles of hydrogen atoms in each sample. a. \(0.0885 \mathrm{~mol} \mathrm{C}_{4} \mathrm{H}_{10}\) b. \(1.3 \mathrm{~mol} \mathrm{CH}_{4}\) c. \(2.4 \mathrm{~mol} \mathrm{C}_{6} \mathrm{H}_{12}\) d. \(1.87 \mathrm{~mol} \mathrm{C}_{8} \mathrm{H}_{18}\)

Determine the number of moles of oxygen atoms in each sample. a. \(4.88 \mathrm{~mol} \mathrm{H}_{2} \mathrm{O}_{2}\) b. \(2.15 \mathrm{~mol} \mathrm{~N}_{2} \mathrm{O}\) c. \(0.0237 \mathrm{~mol} \mathrm{H}_{2} \mathrm{CO}_{3}\) d. \(24.1 \mathrm{~mol} \mathrm{CO}_{2}\)

Calculate the mass (in kilograms) of chlorine in \(25 \mathrm{~kg}\) of each chlorofluorocarbon (CFC). a. \(\mathrm{CF}_{2} \mathrm{Cl}_{2}\) b. \(\mathrm{CFCl}_{3}\) c. \(C_{2} F_{3} CI_{3}\) d. \(\mathrm{CF}_{3} \mathrm{Cl}\)

A chemist decomposes samples of several compounds; the masses of their constituent elements are listed. Calculate the empirical formula for each compound. a. \(1.651 \mathrm{~g} \mathrm{Ag}, 0.1224 \mathrm{~g} \mathrm{O}\) b. \(0.672 \mathrm{~g} \mathrm{Co}, 0.569 \mathrm{~g} \mathrm{As}, 0.486 \mathrm{~g} \mathrm{O}\) c. \(1.443 \mathrm{~g} \mathrm{Se}, 5.841 \mathrm{~g} \mathrm{Br}\)

A chemist decomposes samples of several compounds; the masses of their constituent elements are listed. Calculate the empirical formula for each compound. a. \(1.245 \mathrm{~g} \mathrm{Ni}, 5.381 \mathrm{~g} \mathrm{I}\) b. \(2.677 \mathrm{~g} \mathrm{Ba}, 3.115 \mathrm{~g} \mathrm{Br}\) c. \(2.128 \mathrm{~g} \mathrm{Be}, 7.557 \mathrm{~g} \mathrm{~S}, 15.107 \mathrm{~g} \mathrm{O}\)

Calculate the empirical formula for each stimulant based on its elemental mass percent composition. a. nicotine (found in tobacco leaves): C \(74.03 \%,\) H \(8.70 \%\), N \(17.27 \%\) b. caffeine (found in coffee beans): C \(49.48 \%,\) H \(5.19 \%\), \(\mathrm{N} 28.85 \%, \mathrm{O} 16.48 \%\)

Calculate the empirical formula for each natural flavor based on its elemental mass percent composition. a. methyl butyrate (component of apple taste and smell): \(\mathrm{C} 58.80 \%, \mathrm{H} 9.87 \%, \mathrm{O} 31.33 \%\) b. vanillin (responsible for the taste and smell of vanilla): \(\mathrm{C} 63.15 \%, \mathrm{H} 5.30 \%, \mathrm{O} 31.55 \%\)

The elemental mass percent composition of ascorbic acid (vita\(\min \mathrm{C})\) is \(40.92 \% \mathrm{C}, 4.58 \% \mathrm{H},\) and \(54.50 \%\) O. Determine the empirical formula of ascorbic acid.

A 45.2 -mg sample of phosphorus reacts with selenium to form \(131.6 \mathrm{mg}\) of the selenide. Determine the empirical formula of phosphorus selenide.

From the given empirical formula and molar mass, find the molecular formula of each compound. a. \(\mathrm{C}_{6} \mathrm{H}_{7} \mathrm{~N}, 186.24 \mathrm{~g} / \mathrm{mol}\) b. \(\mathrm{C}_{2} \mathrm{HCl}, 181.44 \mathrm{~g} / \mathrm{mol}\) c. \(\mathrm{C}_{5} \mathrm{H}_{10} \mathrm{NS}_{2}, 296.54 \mathrm{~g} / \mathrm{mol}\)

From the given molar mass and empirical formula of several compounds, find the molecular formula of each compound. a. \(\mathrm{C}_{4} \mathrm{H}_{9}, 114.22 \mathrm{~g} / \mathrm{mol}\) b. \(\mathrm{CCl}, 284.77 \mathrm{~g} / \mathrm{mol}\) c. \(\mathrm{C}_{3} \mathrm{H}_{2} \mathrm{~N}, 312.29 \mathrm{~g} / \mathrm{mol}\)

Combustion analysis of naphthalene, a hydrocarbon used in mothballs, produces \(8.80 \mathrm{~g} \mathrm{CO}_{2}\) and \(1.44 \mathrm{~g} \mathrm{H}_{2} \mathrm{O} .\) Calculate the empirical formula of naphthalene.

The foul odor of rancid butter is due largely to butyric acid, a compound containing carbon, hydrogen, and oxygen. Combustion analysis of a \(4.30-\mathrm{g}\) sample of butyric acid produces \(8.59 \mathrm{~g} \mathrm{CO}_{2}\) and \(3.52 \mathrm{~g} \mathrm{H}_{2} \mathrm{O} .\) Determine the empirical formula of butyric acid.

Tartaric acid is the white, powdery substance that coats tart candies such as Sour Patch Kids. Combustion analysis of a \(12.01-\mathrm{g}\) sample of tartaric acid-which contains only carbon, hydrogen, and oxygen-produces \(14.08 \mathrm{~g} \mathrm{CO}_{2}\) and \(4.32 \mathrm{~g} \mathrm{H}_{2} \mathrm{O}\). Determine the empirical formula of tartaric acid.

Classify each hydrocarbon as an alkane, alkene, or alkyne. a. \(\mathrm{H}_{2} \mathrm{C}=\mathrm{CH}-\mathrm{CH}_{3}\) b. \(\mathrm{H}_{3} \mathrm{C}-\mathrm{CH}_{2}-\mathrm{CH}_{3}\) c. \(\mathrm{HC} \equiv \mathrm{C}-\mathrm{CH}_{3}\) d. \(\mathrm{H}_{3} \mathrm{C}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{3}\)

Write the formula based on the name, or the name based on the formula, for each hydrocarbon. a. \(\mathrm{CH}_{3} \mathrm{CH}_{3}\) b. pentane c. \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}\) d. heptane

Determine the chemical formula of each compound and then use it to calculate the mass percent composition of each constituent element. a. potassium chromate b. lead(II) phosphate c. sulfurous acid d. cobalt(II) bromide

Determine the chemical formula of each compound and then use it to calculate the mass percent composition of each constituent element. a. perchloric acid b. phosphorus pentachloride c. nitrogen triiodide d. carbon dioxide

A Freon leak in the air-conditioning system of a large building releases \(12 \mathrm{~kg}\) of \(\mathrm{CHF}_{2} \mathrm{Cl}\) per month. If the leak is allowed to continue, how many kilograms of Cl will be emitted into the atmosphere each year?

A metal (M) forms a compound with the formula \(\mathrm{MCl}_{3}\). If the compound contains \(65.57 \% \mathrm{Cl}\) by mass, what is the identity of the metal?

A metal (M) forms an oxide with the formula \(\mathrm{M}_{2} \mathrm{O}\). If the oxide contains \(16.99 \%\) O by mass, what is the identity of the metal?

Estradiol is a female sexual hormone that is responsible for the maturation and maintenance of the female reproductive system. Elemental analysis of estradiol gives the following mass percent composition: \(\mathrm{C} 79.37 \%, \mathrm{H} 8.88 \%, \mathrm{O} 11.75 \% .\) The molar mass of estradiol is \(272.37 \mathrm{~g} / \mathrm{mol}\). Find the molecular formula of estradiol.

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

Combustion analysis of a 13.42 -g sample of equilin (which contains only carbon, hydrogen, and oxygen) produces \(39.61 \mathrm{~g} \mathrm{CO}_{2}\) and \(9.01 \mathrm{~g} \mathrm{H}_{2} \mathrm{O} .\) The molar mass of equilin is \(268.34 \mathrm{~g} / \mathrm{mol}\). Find its molecular formula.

Estrone, which contains only carbon, hydrogen, and oxygen, is a female sexual hormone in the urine of pregnant women. Combustion analysis of a 1.893-g sample of estrone produces \(5.545 \mathrm{~g}\) of \(\mathrm{CO}_{2}\) and \(1.388 \mathrm{~g} \mathrm{H}_{2} \mathrm{O} .\) The molar mass of estrone is \(270.36 \mathrm{~g} / \mathrm{mol} .\) Find its molecular formula.

Epsom salts is a hydrated ionic compound with the following formula: \(\mathrm{MgSO}_{4} \cdot x \mathrm{H}_{2} \mathrm{O} .\) A 4.93-g sample of Epsom salts is heated to drive off the water of hydration. The mass of the sample after complete dehydration is \(2.41 \mathrm{~g}\). Find the number of waters of hydration \((x)\) in Epsom salts.

A hydrate of copper(II) chloride has the following formula: \(\mathrm{CuCl}_{2} \cdot x \mathrm{H}_{2} \mathrm{O} .\) The water in a \(3.41-\mathrm{g}\) sample of the hydrate is driven off by heating. The remaining sample has a mass of \(2.69 \mathrm{~g}\) Find the number of waters of hydration \((x)\) in the hydrate.

Researchers obtained 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 \(\mathrm{O}_{2}\) forms \(8.49 \mathrm{~g}\) of \(\mathrm{CO}_{2}\) and \(2.14 \mathrm{~g} \mathrm{H}_{2} \mathrm{O}\). Another \(2.35-\mathrm{g}\) sample contains \(0.199 \mathrm{~g}\) of \(\mathrm{N}\). The molar mass of benzocaine is \(165 \mathrm{~g} / \mathrm{mol} .\) Find the molar formula of benzocaine.

The chloride of an unknown metal is believed to have the formula \(\mathrm{MCl}_{3}\). A 2.395 -g sample of the compound contains \(3.606 \times 10^{-2} \mathrm{~mol}\mathrm{Cl} .\) Find the atomic mass of \(\mathrm{M}\)

Write the structural formulas of three different compounds that each have the molecular formula \(\mathrm{C}_{5} \mathrm{H}_{12 .}\)

Three pure compounds form when 1.00 -g samples of element \(X\) combine with,respectively, 0.472 g, \(0.630 \mathrm{~g}\), and \(0.789 \mathrm{~g}\) of element \(Z\). The first compound has the formula \(X_{2} Z_{3}\). Find the empirical formulas of the other two compounds.

Because of increasing evidence of damage to the ozone layer, chlorofluorocarbon (CFC) production was banned in 1996. However, many older cars still have air conditioners that use \(\mathrm{CFC}-12\) \(\left(\mathrm{CF}_{2} \mathrm{Cl}_{2}\right) .\) These air conditioners are recharged from stockpiled supplies of CFC-12. Suppose that 100 million automobiles each contain \(1.1 \mathrm{~kg}\) of CFC-12 and leak \(25 \%\) of their CFC-12 into the atmosphere per year. How much chlorine, in kg, is added to the atmosphere each year due to these air conditioners? (Assume two significant figures in your calculations.)

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?

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?

Without doing any calculations, determine which element in each compound has the highest mass percent composition. a. CO b. \(\mathrm{N}_{2} \mathrm{O}\) c. \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\) d. \(\mathrm{NH}_{3}\)

Element \(A\) is an atomic element, and element \(B\) is a diatomic molecular element. Using circles to represent atoms of \(\mathrm{A}\) and squares to represent atoms of \(\mathrm{B}\), draw molecular-level views of each element.

Without doing any calculations, arrange the elements in \(\mathrm{H}_{2} \mathrm{SO}_{4}\) in order of decreasing mass percent composition.

With group members playing 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 \(\mathrm{H}_{2} \mathrm{O}\).

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 \(P_{4}, \mathrm{KCl}, \mathrm{CH}_{4}, \mathrm{Ne},\) and \(\mathrm{NH}_{4} \mathrm{NO}_{3}\)

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