Questions: 83. What is the amount, in moles, of each elemental sample? MISSED THIS? Read Section 2.9; Watch KCV 2.9 a. 11.8 g Ar c. 26.1 g Ta b. 3.55 g Zn d. 0.211 g Li 84. What is the mass, in grams, of each elemental sample? a. 2.3 x 10^-3 mol Sb b. 0.0355 mol Ba c. 43.9 mol Xe d. 1.3 mol W 85. How many silver atoms are there in 3.78 g of silver?

Solution Steps

To find the number of moles of an element, use the formula:

\[ \text{moles} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}} \]

• Molar mass of Ar (Argon) = 39.95 g/mol
• Moles of Ar = \(\frac{11.8 \, \text{g}}{39.95 \, \text{g/mol}} = 0.2953 \, \text{mol}\)

• Molar mass of Zn (Zinc) = 65.38 g/mol
• Moles of Zn = \(\frac{3.55 \, \text{g}}{65.38 \, \text{g/mol}} = 0.0543 \, \text{mol}\)

• Molar mass of Ta (Tantalum) = 180.95 g/mol
• Moles of Ta = \(\frac{26.1 \, \text{g}}{180.95 \, \text{g/mol}} = 0.1442 \, \text{mol}\)

• Molar mass of Li (Lithium) = 6.94 g/mol
• Moles of Li = \(\frac{0.211 \, \text{g}}{6.94 \, \text{g/mol}} = 0.0304 \, \text{mol}\)

To find the mass of an element, use the formula:

\[ \text{mass (g)} = \text{moles} \times \text{molar mass (g/mol)} \]

• Molar mass of Sb (Antimony) = 121.76 g/mol
• Mass of Sb = \(2.3 \times 10^{-3} \, \text{mol} \times 121.76 \, \text{g/mol} = 0.2801 \, \text{g}\)

• Molar mass of Ba (Barium) = 137.33 g/mol
• Mass of Ba = \(0.0355 \, \text{mol} \times 137.33 \, \text{g/mol} = 4.8762 \, \text{g}\)

• Molar mass of Xe (Xenon) = 131.29 g/mol
• Mass of Xe = \(43.9 \, \text{mol} \times 131.29 \, \text{g/mol} = 5764.631 \, \text{g}\)

• Molar mass of W (Tungsten) = 183.84 g/mol
• Mass of W = \(1.3 \, \text{mol} \times 183.84 \, \text{g/mol} = 239.0 \, \text{g}\)

To find the number of atoms, use Avogadro's number (\(6.022 \times 10^{23}\) atoms/mol):

\[ \text{atoms} = \text{moles} \times 6.022 \times 10^{23} \, \text{atoms/mol} \]

• Molar mass of Ag (Silver) = 107.87 g/mol
• Moles of Ag = \(\frac{3.78 \, \text{g}}{107.87 \, \text{g/mol}} = 0.0350 \, \text{mol}\)
• Number of Ag atoms = \(0.0350 \, \text{mol} \times 6.022 \times 10^{23} \, \text{atoms/mol} = 2.108 \times 10^{22} \, \text{atoms}\)

Final Answer