Chapter 10

Zinc (Zn) is used to form a corrosion-inhibiting surface on galvanized steel. Determine the number of Zn atoms in 2.50 mol of Zn.

Calculate the number of molecules in 11.5 mol of water \(\left(\mathrm{H}_{2} \mathrm{O}\right)\)

Silver nitrate \(\left(A g N O_{3}\right)\) is used to make several different silver halides used in photographic films. How many formula units of \(A g N O_{3}\) are there in 3.25 mol of \(A g N O_{3} ?\)

How many moles contain each of the following? a. \(5.75 \times 10^{24}\) atoms Al \(\quad\) b. \(2.50 \times 10^{20}\) atoms Fe

Challenge Identify the representative particle for each formula, and convert the given number of representative particles to moles. a. \(3.75 \times 10^{24} \mathrm{CO}_{2} \quad\) b. \(3.58 \times 10^{23} \mathrm{ZnCl}_{2}\)

Explain why chemists use the mole.

State the mathematical relationship between Avogadro's number and 1 mol.

List the conversion factors used to convert between particles and moles.

Explain how a mole is similar to a dozen.

Calculate the mass of 0.25 mol of carbon-12 atoms.

Calculate the number of representative particles of each substance. \begin{equation}\begin{array}{ll}{\text { a. } 11.5 \mathrm{mol} \mathrm{Ag}} & {\text { c. } 0.150 \mathrm{mol} \mathrm{NaCl}} \\ {\text { b. } 18.0 \mathrm{mol} \mathrm{H}_{2} \mathrm{O}} & {\text { d. } 1.35 \times 10^{-2} \mathrm{mol} \mathrm{CCH}_{4}}\end{array}\end{equation}

Arrange these three samples from smallest to largest in terms of number of representative particles: \(1.25 \times 10^{25}\) atoms of zinc (Zn), 3.56 mol of iron (Fe), and \(6.78 \times 10^{22}\) molecules of glucose \(\left(C_{6} \mathrm{H}_{12} \mathrm{O}_{6}\right)\)

Determine the mass in grams of each of the following a. 3.57 mol Al b. 42.6 mol Si

What is the mass in grams of each of the following? \begin{equation}\begin{array}{l}{\text { a. } 6.02 \times 10^{24} \text { atoms Bi }} \\ {\text { b. } 1.00 \times 10^{24} \text { atoms Mn }} \\\ {\text { c. } 3.40 \times 10^{22} \text { atoms He }} \\ {\text { d. } 1.50 \times 10^{15} \text { atoms } \mathrm{N}} \\ {\text { e. } 1.50 \times 10^{15} \text { atoms } U}\end{array}\end{equation}

Explain how molar mass relates the mass of an atom to the mass of a mole of atoms.

Arrange these quantities from smallest to largest in terms of mass: 1.0 mol of \(\mathrm{Ar}, 3.0 \times 10^{24}\) atoms of \(\mathrm{Ne},\) and 20 \(\mathrm{g}\) of \(\mathrm{Kr}\) .

Identify the quantity that is calculated by dividing the molar mass of an element by Avogadro's number.

Design a concept map that shows the conversion factors needed to convert between mass, moles, and number of particles.

Zinc chloride \(\left(\mathrm{ZnCl}_{2}\right)\) is used in soldering flux, an alloy used to join two metals together. Determine the moles of \(\mathrm{Cl}^{-}\) ions in 2.50 \(\mathrm{mol} \mathrm{ZnCl}_{2}\) .

Plants and animals depend on glucose \(\left(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\right)\) as an energy source. Calculate the number of moles of each element in 1.25 mol \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\) .

Iron(III) sulfate \(\left[\mathrm{Fe}_{2}\left(\mathrm{SO}_{4}\right)_{3}\right]\) is sometimes used in the water purification process. Determine the number of moles of sulfate ions present in 3.00 mol of \(\mathrm{Fe}_{2}\left(\mathrm{SO}_{4}\right)_{3}\).

Challenge Calculate the number of moles of hydrogen atoms in \(1.15 \times 10^{1}\) mol of water. Express the answer in scientific notation.

Determine the molar mass of each ionic compound. \begin{equation}\begin{array}{ll}{\text { a. } \mathrm{NaOH}} & {\text { b. } \mathrm{CaCl}_{2}} & {\text { c. } \mathrm{KC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}}\end{array}\end{equation}

Calculate the molar mass of each molecular compound. \begin{equation}a. \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH} \quad \text { b. HCN } \quad \text { c. } \mathrm{CCl}_{4}\end{equation}

Identify each substance as a molecular compound or an ionic compound, and then calculate its molar mass. \begin{equation}a . {Sr}\left(\mathrm{NO}_{3}\right)_{2}\end{equation} \begin{equation}b. \left(\mathrm{NH}_{4}\right)_{3} \mathrm{PO}_{4}\end{equation} \begin{equation}\mathbf{c} . \mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\end{equation}

The United States chemical industry produces more sulfuric acid \(\left(\mathrm{H}_{2} \mathrm{SO}_{4}\right),\) in terms of mass, than any other chemical. What is the mass of 3.25 \(\mathrm{mol}\) of \(\mathrm{H}_{2} \mathrm{SO}_{4}\) ?

Write the chemical formula for potassium permanganate, and then calculate the mass in grams of 2.55 mol of the compound.

Identify each as an ionic or molecular compound and convert the given mass to moles. Express your answers in scientific notation. \begin{equation}a. 2.50 \mathrm{kg} \quad \mathrm{Fe}_{2} \mathrm{O}_{3} \quad \text { b. } 25.4 \mathrm{mg} \quad \mathrm{PbCl}_{4}\end{equation}

Ethanol \(\left(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\right),\) a domestically produced fuel source, is often blended with gasoline. A sample of ethanol has a mass of 45.6 \(\mathrm{g} .\) \begin{equation}\begin{array}{l}{\text { a. How many carbon atoms does the sample contain? }} \\ {\text { b. How many hydrogen atoms are present? }} \\\ {\text { c. How many oxygen atoms are present? }}\end{array}\end{equation}

A sample of sodium sulfite \(\left(\mathrm{Na}_{2} \mathrm{SO}_{3}\right)\) has a mass of 2.25 \(\mathrm{g}\) \begin{equation}\begin{array}{l}{\text { a. How many } \mathrm{Na}^{+} \text { ions are present? }} \\ {\text { b. How many } \mathrm{SO}_{3}^{2-} \text { ions are present? }} \\ {\text { c. What is the mass in grams of one formula unit of } \mathrm{Na}_{2} \mathrm{SO}_{3} ?}\end{array}\end{equation}

A sample of sodium sulfite \(\left(\mathrm{Na}_{2} \mathrm{SO}_{3}\right)\) has a mass of 2.25 \(\mathrm{g}\) \begin{equation}\begin{array}{l}{\text { a. How many } \mathrm{Na}^{+} \text { ions are present? }} \\ {\text { b. How many } \mathrm{SO}_{3}^{2-} \text { ions are present? }} \\ {\text { c. What is the mass in grams of one formula unit of } \mathrm{Na}_{2} \mathrm{SO}_{3} ?}\end{array}\end{equation}

What mass of sodium chloride (NaCl) contains \(4.59 \times 10^{24}\) formula units?

A sample of silver chromate has a mass of 25.8 g. \begin{equation}\begin{array}{l}{\text { a. Write the formula for silver chromate. }} \\ {\text { b. How many cations are present in the sample? }} \\\ {\text { c. How many anions are present in the sample? }} \\ {\text { d. What is the mass in grams of one formula unit of silver chromate? }}\end{array}\end{equation}

Describe how to determine the molar mass of a compound.

Identify the conversion factors needed to convert between the number of moles and the mass of a compound.

Apply How many moles of \(\mathrm{K}, \mathrm{C},\) and 0 atoms are there in 1 \(\mathrm{mol}\) of \(\mathrm{K}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\) ?

Calculate Calcium carbonate is the calcium source for many vitamin tablets. The recommended daily allowance of calcium is 1000 \(\mathrm{mg}\) of \(\mathrm{Ca}^{2}+\) ions. How many moles of \(\mathrm{Ca}^{2+}\) does 1000 \(\mathrm{mg}\) represent?

Design a bar graph that will show the number of moles of each element present in 500 g of a particular form of dioxin \(\left(\mathrm{C}_{12} \mathrm{H}_{4} \mathrm{Cl}_{4} \mathrm{O}_{2}\right),\) a powerful poison.

What is the percent composition of phosphoric acid \(\left(\mathrm{H}_{3} \mathrm{PO}_{4}\right) ?\)

Which has the larger percent by mass of sulfur, \(\mathrm{H}_{2} \mathrm{SO}_{3}\) or \(\mathrm{H}_{2} \mathrm{S}_{2} \mathrm{O}_{8} ?\)

Calcium chloride \(\left(\mathrm{CaCl}_{2}\right)\) is sometimes used as a de- icer. Calculate the percent by mass of each element in \(\mathrm{CaCl}_{2}\)

Sodium sulfate is used in the manufacture of detergents. \begin{equation}\begin{array}{l}{\text { a. Identify each of the component elements of sodium sulfate, and write the compound's chemical formula. }} \\\ {\text { b. Identify the compound as ionic or covalent. }} \\ {\text { c. Calculate the percent by mass of each element in sodium sulfate. }}\end{array}\end{equation}

\begin{equation} \begin{array}{l}{\text { Determine the empirical formula for a compound that contains } 35.98 \% \text { aluminum and }} \\ {64.02 \% \text { sulfur. }}\end{array} \end{equation}

Propane is a hydrocarbon, a compound composed only of carbon and hydrogen. It is 81.82\(\%\) carbon and 18.18\(\%\) hydrogen. What is the empirical formula?

Challenge Aspirin is the world's most-often used medication. The chemical analysis of aspirin indicates that the molecule is \(60.00 \%\) carbon, \(4.44 \%\) hydrogen, and \(35.56 \%\) oxygen. Determine the empirical formula for aspirin.

A compound was found to contain 49.98 g of carbon and 10.47 g of hydrogen. The molar mass of the compound is 58.12 \(\mathrm{g} / \mathrm{mol}\) . Determine the molecular formula.

A colorless liquid composed of \(46.68 \%\) nitrogen and \(53.32 \%\) oxygen has a molar mass of \(60.01 \mathrm{~g} / \mathrm{mol} .\) What is the molecular formula?

When an oxide of potassium is decomposed, 19.55 g of \(\mathrm{K}\) and 4.00 \(\mathrm{g}\) of \(\mathrm{O}\) are obtained. What is the empirical formula for the compound?

A classmate tells you that experimental data shows a compound's molecular formula to be 2.5 times its empirical formula. Is he correct? Explain.

Analysis of a compound composed of iron and oxygen yields 174.86 g of Fe and 75.14 g of O. What is the empirical formula for this compound?