Chapter 10

An oxide of aluminum contains 0.545 g of Al and 0.485 g of O. Find the empirical formula for the oxide.

Explain how percent composition data for a compound are related to the masses of the elements in the compound.

Explain how you can find the mole ratio in a chemical compound.

Apply The molar mass of a compound is twice that of its empirical formula. How are the compound's molecular and empirical formulas related?

Analyze Hematite \(\left(\mathrm{Fe}_{2} \mathrm{O}_{3}\right)\) and magnetite \(\left(\mathrm{F}_{3} \mathrm{O}_{4}\right)\) are two ores used as sources of iron. Which ore provides the greater percent of iron per kilogram?

An \(11.75-9\) sample of a common hydrate of cobalt(ll) chloride is heated. After heating, 0.0712 mol of anhydrous cobalt chloride remains. What is the formula and the name of this hydrate?

Calculate the mass of the water of hydration if a hydrate loses 0.025 mol of \(\mathrm{H}_{2} \mathrm{O}\) when heated.

Arrange these hydrates in order of increasing percent water content: \(\operatorname{MgSO}_{4} \cdot 7 \mathrm{H}_{2} \mathrm{O}, \mathrm{Ba}(\mathrm{OH})_{2} \cdot 8 \mathrm{H}_{2} \mathrm{O},\) and \(\mathrm{CoCl}_{2} \cdot 6 \mathrm{H}_{2} \mathrm{O}\)

What is the numerical value of Avogadro's number?

How many atoms of potassium does 1 mol of potassium contain?

Compare a mole of Ag-108 and a mole of Pt-195 using atoms, protons, electrons, and neutrons.

Why is the mole an important unit to chemists?

Explain how Avogadro's number is used as a conversion factor.

Design a flowchart that could be used to help convert particles to moles or moles to particles.

Determine the number of representative particlesin each substance \begin{equation}\begin{array}{l}{\text { a. } 0.250 \text { mol of siver }} \\\ {\text { b. } 8.56 \times 10^{-3} \text { mol of sodium chloride }} \\\ {\text { c. } 35.3 \text { mol of carbon dioxide }} \\ {\text { d. } 0.425 \text { mol of nitrogen }\left(\mathrm{N}_{2}\right)}\end{array}\end{equation}

Determine the number of representative particles in each substance \begin{equation}\begin{array}{ll}{\text { a. } 4.45 \text { mol of } \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}} & {\text { c. } 2.24 \mathrm{mol} \text { of } \mathrm{H}_{2}} \\ {\text { b. } 0.250 \mathrm{mol}} {\text { of } \mathrm{KNO}_{3}} & {\text { d. } 9.56 \mathrm{mol} \text { of } \mathrm{Zn}}\end{array}\end{equation}

How many molecules are contained in each compound? \begin{equation}\begin{array}{l}{\text { a. } 1.35 \text { mol of carbon disulfide }\left(\mathrm{CS}_{2}\right)} \\ {\text { b. } 0.254 \text { mol of diarsenic trioxide }\left(\mathrm{As}_{2} \mathrm{O}_{3}\right)} \\ {\text { c. } 1.25 \text { mol of water }} \\ {\text { d. } 150.0 \text { mol of } \mathrm{HCl}}\end{array}\end{equation}

Determine the number of moles in each substance. \begin{equation}\begin{array}{l}{\text { a. } 3.25 \times 10^{20} \text { atoms of lead }} \\ {\text { b. } 4.96 \times 10^{24} \text { molecules of glucose }} \\ {\text { c. } 1.56 \times 10^{23} \text { formula units of sodium hydroxide }} \\ {\text { d. } 1.25 \times 10^{25} \text { copper (II) ions }}\end{array}\end{equation}

Perform the following conversions \begin{equation}\begin{array}{l}{\text { a. } 1.51 \times 10^{15} \text { atoms of Si to mol of Si }} \\ {\text { b. } 4.25 \times 10^{-2} \text { mol of } \mathrm{H}_{2} \mathrm{SO}_{4} \text { to molecules of } \mathrm{H}_{2} \mathrm{SO}_{4}} \\ {\text { c. } 8.95 \times 10^{25} \text { molecules of } \mathrm{CCl}_{4} \text { to mol of } \mathrm{CCl}_{4}} \\ {\text { d. } 5.90 \mathrm{mol} \text { of Ca to atoms of } \mathrm{Ca}}\end{array}\end{equation}

How many moles contain the given quantity? \begin{equation}\begin{array}{l}{\text { a. } 1.25 \times 10^{15} \text { molecules of carbon dioxide }} \\ {\text { b. } 3.59 \times 10^{21} \text { formula units of sodium nitrate }} \\ {\text { c. } 2.89 \times 10^{27} \text { formula units of calcium carbonate }}\end{array}\end{equation}

RDA of Selenium The recommended daily allowance \((\mathrm{RDA})\) of selenium in your diet is \(8.87 \times 10^{-4} \mathrm{mol} .\) How many atoms of selenium is this?

Jewelry A bracelet containing 0.200 mol metal atoms is 75\(\%\) gold. How many particles of gold atoms are in the bracelet?

Snowflakes A snowflake contains \(1.9 \times 10^{18}\) molecules of water. How many moles of water does it contain?

If you could count two atoms every second, how long would it take you to count a mole of atoms? Assume that you counted continually for 24 hours every day. How does the time you calculated compare with the age of Earth, which is estimated to be \(4.5 \times 10^{9}\) years old?

Chlorophyll The green color of leaves is due to the presence of chlorophyll, \(\mathrm{C}_{55} \mathrm{H}_{72} \mathrm{O}_{5} \mathrm{N}_{4} \mathrm{Mg} .\) A fresh leaf was found to have \(1.5 \times 10^{-5} \mathrm{mol}\) of chlorophyll per \(\mathrm{cm}^{2} .\) How many chlorophyll molecules are in 1 \(\mathrm{cm}^{2} ?\)

Explain the difference between atomic mass (amu) and molar mass (g).

Which contains more atoms, a mole of silver atoms or a mole of gold atoms? Explain your answer.

Which has more mass, a mole of potassium or a mole of sodium? Explain your answer.

Explain how you would convert from number of atoms of a specific element to its mass.

Discuss the relationships that exist between the mole, molar mass, and Avogadro's number.

Barbed wire is often made of steel, which is primarily iron, and coated with zinc. Compare the number of particles and the mass of 1 mol of each.

Calculate the mass of each element. \begin{equation}\begin{array}{ll}{\text { a. } 5.22 \text { mol of } \mathrm{He}} & {\text { c. } 2.22 \mathrm{mol} \text { of Ti }} \\ {\text { b. } 0.0455 \text { mol of } \mathrm{Ni}} & {\text { d. } 0.00566 \mathrm{mol} \text { of Ge }}\end{array}\end{equation}

Convert each to mass in grams. \begin{equation}\begin{array}{l}{\text { a. } 4.22 \times 10^{15} \text { atoms } \mathrm{U}} \\ {\text { b. } 8.65 \times 10^{25} \text { atoms } \mathrm{H}} \\ {\text { c. } 1.25 \times 10^{22} \text { atoms } \mathrm{O}} \\\ {\text { d. } 4.44 \times 10^{23} \text { atoms } \mathrm{Pb}}\end{array}\end{equation}

Arrange from least to most in moles: \(3.00 \times 10^{24}\) atoms Ne, 4.25 mole \(\mathrm{Ar}, 2.69 \times 10^{24}\) atoms \(\mathrm{Xe}, 65.96 \mathrm{g} \mathrm{Kr}\) .

Balance Precision A sensitive electronic balance can detect masses of \(1 \times 10^{-8}\) g. How many atoms of silver would be in a sample having this mass?

A sample of a compound contains 3.86 g of sulfur and 4.08 g of vanadium. How many atoms of sulfur and vanadium does the compound contain?

Which has more atoms, 10.0 g of C or 10.0 g of Ca? How many atoms does each have?

Which has more atoms, 10.0 mol of C or 10.0 mol of Ca? How many atoms does each have?

A mixture contains 0.250 mol of Fe and 1.20 g of C. What is the total number of atoms in the mixture?

Air contains several gases. When resting, every breath you take contains approximately 0.600 g of air. If argon makes up 0.934% of the air, calculate the number of argon atoms inhaled with each breath.

What information is provided by the formula for potas- sium chromate \(\left(\mathrm{K}_{2} \mathrm{CrO}_{4}\right) ?\)

Explain how you determine the molar mass of a compound.

Why can molar mass be used as a conversion factor?

Which of these contains the most moles of carbon atoms per mole of the compound: ascorbic acid \(\left(\mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{6}\right)\) glycerin \(\left(\mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O}_{3}\right),\) or vanillin \(\left(\mathrm{C}_{8} \mathrm{H}_{8} \mathrm{O}_{3}\right) ?\) Explain.

How many moles of oxygen atoms are contained in each compound? \begin{equation}\begin{array}{l}{\text { a. } 2.50 \text { mol of } \mathrm{KMnO}_{4}} \\ {\text { b. } 45.9 \mathrm{mol} \text { of } \mathrm{CO}_{2}} \\ {\text { c. } 1.25 \times 10^{-2} \mathrm{mol} \text { of } \mathrm{CuSO}_{4} \cdot 5 \mathrm{H}_{2} \mathrm{O}}\end{array}\end{equation}

How many carbon tetrachloride \(\left(\mathrm{CCl}_{4}\right)\) molecules are in 3.00 \(\mathrm{mol}\) of \(\mathrm{CCl}_{4} ?\) How many carbon atoms? How many chlorine atoms? How many total atoms?

Determine the molar mass of each compound. a. nitric acid \(\left(\mathrm{HNO}_{3}\right)\) b. ammonium nitrate \(\left(\mathrm{NH}_{4} \mathrm{NO}_{3}\right)\) c. zinc oxide \((\mathrm{ZnO})\) d. cobalt chloride \(\left(\mathrm{CoCl}_{2}\right)\)

Garlic Determine the molar mass of allyl sulfide, the compound responsible for the smell of garlic. The chemical formula of allyl sulfide is \(\left(\mathrm{C}_{3} \mathrm{H}_{5}\right)_{2} \mathrm{S}\) .

Acne Benzoyl peroxide \(\left(\mathrm{C}_{14} \mathrm{H}_{10} \mathrm{O}_{4}\right)\) is a substance used as an acne medicine. What is the mass in grams of \(3.50 \times 10^{-2} \mathrm{mol} \mathrm{C}_{14} \mathrm{H}_{10} \mathrm{O}_{4} ?\)

What is the mass of a mole of electrons if one electron has a mass of \(9.11 \times 10^{-28} \mathrm{g} ?\)