Aluminum has an atomic radius of 143 \(\mathrm{pm}\) and forms a solid with a cubic closest packed structure. Calculate the density of solid aluminum in \(\mathrm{g} / \mathrm{cm}^{3}\) .

Short Answer

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\(a \approx 405.2\, \text{pm}\) #tag_title# Step 3: Calculate the volume of the unit cell #tag_content# Now that we have the edge length, we can calculate the volume of the unit cell (V): \(V = a^3\) Substitute the edge length (a) into the formula: \(V = (405.2\, \text{pm})^3\) Calculating the volume (V): \(V \approx 6.68 \times 10^7\, \text{pm}^3\) #tag_title# Step 4: Convert volume to cm³ #tag_content# To calculate the density in g/cm³, we need to convert the volume from pm³ to cm³: \(1\, \text{pm} = 10^{-10} \, \text{cm}\) \(V \approx 6.68 \times 10^7\, \text{pm}^3 \times (10^{-10}\, \text{cm} / \text{pm})^3\) Calculating the volume in cm³: \(V \approx 6.68 \times 10^{-23}\, \text{cm}^3\) #tag_title# Step 5: Determine the molar mass and Avogadro's number #tag_content# The molar mass of aluminum is 26.98 g/mol. Avogadro's number (N) is approximately \(6.022 \times 10^{23}\) particles/mol. #tag_title# Step 6: Calculate the density #tag_content# The density (ρ) of solid aluminum can be calculated using the formula: \(\rho = \frac{4 \times M_{\text{Al}}}{N \times V}\) Substituting the values found previously: \(\rho \approx \frac{4 \times 26.98\, \text{g/mol}}{6.022 \times 10^{23} \, \text{particles/mol} \times 6.68 \times 10^{-23}\, \text{cm}^3}\) Calculating the density (ρ): \(\rho \approx 2.70\, \text{g/cm}^3\) Thus, the density of solid aluminum is approximately 2.70 g/cm³.

Step by step solution

01

Determine the atomic structure and atoms per unit cell

In a cubic closest packed (ccp) structure, also called face-centered cubic (fcc), the atoms are packed as close together as possible. In this arrangement, each unit cell contains 4 atoms.
02

Find the edge length of the unit cell

To calculate the edge length (a) of the unit cell, we must first recognize that in an fcc structure, the face diagonal is equal to 4 times the atomic radius (r). We can use the Pythagorean theorem twice since the face diagonal cuts through the unit cell: \(a^2 + a^2 = (\frac{4r}{\sqrt{2}})^2 => a = 2r\sqrt{2}\) We substitute the atomic radius of aluminum (r = 143 pm) into the formula: \(a = 2(143\, \text{pm})\sqrt{2}\) Calculating the edge length (a):

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