Chapter 10

Determine the percent composition of \(\mathrm{MgCO}_{3} \cdot 5 \mathrm{H}_{2} \mathrm{O}\) and draw a pie graph to represent the hydrate.

What is the formula and name of a hydrate that is 85.3% barium chloride and 14.7% water?

Gypsum is hydrated calcium sulfate. A 4.89-g sample of this hydrate was heated. After the water was removed, 3.87 g anhydrous calcium sulfate remained. Determine the formula for this hydrate and name the compound.

A 1.628-g sample of a hydrate of magnesium iodide is heated until its mass is reduced to 1.072 g and all water has been removed. What is the formula of the hydrate?

Borax Hydrated sodium tetraborate \(\left(\mathrm{Na}_{2} \mathrm{B}_{4} \mathrm{O}_{7} \cdot \mathrm{xH}_{2} \mathrm{O}\right)\) is commonly called borax. Chemical analysis indicates that this hydrate is 52.8\(\%\) sodium tetraborate and 47.2\(\%\) water. Determine the formula and name the hydrate.

Rank samples \(A-D\) from least number of atoms to greatest number of atoms. A: 1.0 \(\mathrm{mol}\) of \(\mathrm{H}_{2} ; \mathrm{B} : 0.75 \mathrm{mol}\) of \(\mathrm{H}_{2} \mathrm{O} ; \mathrm{C} : 1.5 \mathrm{mol}\) of \(\mathrm{NaCl} ; \mathrm{D} : 0.50 \mathrm{mol}\) of \(\mathrm{Ag}_{2} \mathrm{S}\)

How many grams of \(\mathrm{CoCl}_{2} \cdot 6 \mathrm{H}_{2} \mathrm{O}\) must you measure out in a container to have exactly Avogadro's number of particles?

One atom of an unknown element has a mass of \(6.66 \times 10^{-23} \mathrm{g} .\) What is the identity of this element?

Skunks Analysis of skunk spray yields a molecule with 44.77% C, 7.46% H and 47.76% S. What is the chemical formula for this molecule found in the spray from skunks that scientists think is partly responsible for the strong odor?

How many moles are present in 1.00 g of each compound? a. L-tryptophan \(\left(\mathrm{C}_{11} \mathrm{H}_{12} \mathrm{N}_{2} \mathrm{O}_{2}\right),\) an essential amino acid b. magnesium sulfate heptahydrate, also known as Epsom salts c. propane \(\left(\mathrm{C}_{5} \mathrm{H}_{8}\right),\) a fuel

A compound contains 6.0 g of carbon and 1.0 g of hydrogen, and has a molar mass of 42.0 g/mol. What are the compound’s percent composition, empirical formula, and molecular formula?

Which of these compounds has the greatest percent of oxygen by mass: TiO \(_{2}, \mathrm{Fe}_{2} \mathrm{O}_{3},\) or \(\mathrm{Al}_{2} \mathrm{O}_{3} ?\)

Mothballs Naphthalene, commonly found in mothballs, is composed of 93.7% carbon and 6.3% hydrogen. The molar mass of naphthalene is 128 g/mol. Determine the empirical and molecular formulas for naphthalene.

Which of these molecular formulas are also empirical formulas: ethyl ether \(\left(\mathrm{C}_{4} \mathrm{H}_{10} \mathrm{O}\right),\) aspirin \(\left(\mathrm{C}_{9} \mathrm{H}_{8} \mathrm{O}_{4}\right),\) butyl dichloride \(\left(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}_{2}\right),\) glucose \(\left(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\right) ?\)

Apply Concepts A mining company has two possible sources of copper: chalcopyrite (CuFeS \(_{2} )\) and chalcocite \(\left(\mathrm{Cu}_{2} \mathrm{S}\right) .\) If the mining conditions and the extraction of copper from the ore were identical for each of the ores, which ore would yield the greater quantity of copper? Explain your answer.

Graph A YAG, or yttrium aluminum garnet \(\left(\mathrm{Y}_{3} \mathrm{Al}_{5} \mathrm{O}_{12}\right),\) is a synthetic gemstone which has no counterpart in nature. Design a bar graph to indicate the moles of each element present in a 5.67 carat yttrium aluminum garnet. ( carat \(=0.20 \mathrm{g} )\)

Design a concept map that illustrates the mole concept. Include the terms moles, Avogadro’s number, molar mass, number of particles, percent composition, empirical formula, and molecular formula

Two different compounds are composed of Elements \(\mathrm{X}\) and \(\mathrm{Y}\) . The formulas of the compounds are \(\mathrm{X}_{2} \mathrm{Y}_{3}\) and \(\mathrm{XY}\) . A 0.25 mol sample of \(\mathrm{XY}\) has a mass of \(17.96 \mathrm{g},\) and a 0.25 mol sample of \(\mathrm{X}_{2} \mathrm{Y}_{3}\) has a mass of 39.92 \(\mathrm{g}\) . a. What are the atomic masses of elements \(\mathrm{X}\) and \(\mathrm{Y}\) ? b. What are the formulas for the compounds?

Express each answer with the correct number of significant figures. (Chapter 2) a. \(18.23-456.7\) b. \(4.233 \div 0.0131\) c. \((82.44 \times 4.92)+0.125\)

Making Candy A recipe for pralines calls for the candy mixture to be heated until it reaches the "soft ball" stage, at about \(236^{\circ} \mathrm{F}\) . Can a Celsius thermometer with a range of \(-10\) to \(110^{\circ} \mathrm{C}\) be used to determine when the "softball" stage is reached? (Chapter 2)

Contrast atomic number and mass number. Compare these numbers for isotopes of an element. (Chapter 4)

Given the elements Ar, Cs, Br, and Ra, identify those that form positive ions. Explain your answer. (Chapter 7)

Write the formula and name the compound formed when each pair of elements combine. (Chapter 7) a. barium and chlorine b. aluminum and selenium c. calcium and phosphorus

Write balanced equations for each reaction. (Chapter 9) a. Magnesium metal and water combine to form solid magnesium hydroxide and hydrogen gas. b. Dinitrogen tetroxide gas decomposes into nitrogen dioxide gas. c. Aqueous solutions of sulfuric acid and potassium hydroxide undergo a double-replacement reaction.

Natural Gas Natural gas hydrates are chemical compounds known as clathrate hydrates. Research natural gas hydrates and prepare an educational pamphlet for consumers. The pamphlet should discuss the composition and structure of the compounds, the location of the hydrates, their importance to consumers, and the environmental impact of using the hydrates.

Avogadro Research and report on the life of Italian chemist Amedeo Avogadro (1776–1856) and how his work led scientists to determine the number of particles in a mole.

Hydrazine contains 87.45% nitrogen and 12.55% hydrogen, and has a molar mass of 32.04 g/mol. Determine hydrazine’s molecular formula. Record the molecular formula in Table 10.6.