Question

Calculate the mass of a unit cell of copper crystals. (Atomic mass of Cu = 63.54u) ?​

Answer 1

Answer:

254.16 u

Explanation:

Copper crystals form face-centered-cubic crystals, where they contain 1/8th of atoms at each corner of the cube, and, 1/2 atom at each face.

So total atoms = 8 * (1/8)  + 6 *  (1/2)

                         = 1 + 3

                         = 4  atom

Hence,

mass of unit cell = 4 * mass of Cu

                           = 4 * 63.54 u

                           = 254.16 u

In grams,  N is Avagadro's number

mass = 254.15/N = 254.14/(6.022 * 10²³)

        = 42.2 * 10⁻²³ gram

        = 0.422 * 10⁻²¹