USA: +1 (725) 712-1730 
Sign in
Equation for determining the radius of a simple cubic unit ceil is r = l/2 Equation for determining the radius of a face-centered cubic unit cell is r = l Squareroot 2/4 Equation for determining the radius of a body-centered cubic unit cell is r = l Squareroot 3/4 An unknown element crystallizes in a body-centered cubic lattice structure. The edge of the unit cell is 2.86 A. The density of the unknown crystal is 7.92 g/mL. Which of the following expressions can be used to determine the atomic mass of the unknown element? A. (2.86 times 10^-3 cm)^3 times 7.92 g/cm^3 times 6.022 times 10^23 atoms/mol times 1/2 atoms B. 2.86 times 10^-3 cm times 7.92 g/cm^3 times 6.022 times 10^23 atoms/mol times 2 atoms C. (2.86 times 10^-3 cm)^3 times 7.92 g/cm^3 times 1 mol/6.022 times 10^23 atoms times 1/2 atoms D. (2.86 times 10^-3 cm)^3 times 1 cm^2/7.92 g times 6.022 times 10^23 atoms/mol times 1/2 atoms E. None of the above
Expert Answer
length of edge = 2.86 A = 2.86*10^-8 cm
So,
volume of cell = a^3 = ( 2.86*10^-8 cm )^3
mass of unit cell = volume of cell * density
= (2.86*10^-8 cm )^3 * 7.92 g/cm^3
since BCC has 2 atom
mass of 1 atom = mass of unit cell / 2 atoms
= (2.86*10^-8 cm )^3 * 7.92 g/cm^3 * (1/2 atoms)
mass of 1 mol of atoms = mass of 1 atom * 6.022*10^23
mass of 1 mol of atoms = (2.86*10^-8 cm )^3 * 7.92 g/cm^3 * (6.022*10^23 atoms) / 1 mol (1/2 atoms)
This is atomic mass
Answer: A
