chemistry

posted by .

an unknown element crystallizes in a face-centered cubic unit cell. with an edge length of 392.4 pm. The solid has a density of 21.09 g/cm^3. what is atomic weight of solid?

so what i did was :

FC cubic uit --> 4 atoms
edge length--> l = 2*root2*r = 392.4 pm = 392.4 * 10^-8 cm.
d= 21.09 g/cm^3
d= m/l^3

m= l^3 * d

m= 8.2757*10^-5 g

1amu = 1.66054 * 10^-24 g

atomic weight = 4.98 * 10^19 amu.

and that is not the correct answer at all. where am i going wrong? please help :/

the options are :

a) 6.9 amu
b) 241.7 amu
c)74.4 amu
d) 191.8 amu

  • chemistry -

    ryeng i suppose?
    this is a very easy question
    392.4*10-10= x cm
    xcm^3= ycm^3

    ycm^3* 21.09= mass in grams
    since face centered unit cell has 4 atoms
    mass/4, then use the product of that to divide by 1.66*10^-24 = amu
    your result should be 191.84 amu

  • chemistry -

    One place you erred is in the volume. You have a given to you (the edge length) so volume = a^3.

    I agree with Tom's answer although I don't follow all of the work. My answer is 191.77 which rounds to 191.8 and that is one of the answers.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. CHEM

    Info: The atoms of crystalline solid pack together into a three-dimensional array of many small repeating units called unit cells. The simplest of the unit cells are those that have cubic symmetry, with atoms positioned at the corners …
  2. chemistry

    Gallium crystallizes in a primitive cubic unit cell. The length of an edge of this cube is 362 pm. What is the radius of a gallium atom?
  3. Chemistry

    An element crystallizes in a body-centered cubic lattice. The edge of the unit cell is 3.5 Angstrom, and the density of the crystal is 7.39g/cm^3. Calculate the atomic weight of the element. A= ?
  4. science

    The lanthanide metal europium (Eu) forms a crystalline solid with a cubic unit cell of edge length 3.854 Å. The density of europium is 4.408 g cm-3. The crystal structure of solid europium is a. body-centered cubic b. simple cubic …
  5. chemistry

    a metal crystallizes in the face centred cubic cubic crustal structure with a unit cell edge of 5.48 x10 power of -8 cm.the density of the metal is 6.90g per cubic cm. a. what is the mass in grams, of a single atom of this element. …
  6. chemistry

    a metal crystallizes in the face centered cubic crystal structure with a unit cell edge of 5.48 x10 power of -8 cm. the density of the metal is 6.90 g per cubic cm. a. what is the mass (g) of a single atom of this element. b. what …
  7. chemistry

    You are given a small bar of an unknown metal, X. You find the density of the metal to be 11.7 g/cm3. An X-ray diffraction experiment measures the edge of the unit cell as 5.12 angstroms. Assuming the metal crystallizes in a face-centered …
  8. Chemistry

    An element crystallizes in a body-centered cubic lattice. The edge of the unit cell is 2.77 , and the density of the crystal is 8.65 . Find the atomic weight of the element.
  9. Chemistry

    An element crystallizes in a body-centered cubic lattice. The edge of the unit cell is 3.13Å , and the density of the crystal is 7.78g/cm3. Calculate the atomic weight of the element. Please help, thanks
  10. Chemistry

    Element X has a face-centered cubic unit cell structure. If the density of the element is measured to be 12.4 g/cm^3, what is the atomic radius of X?

More Similar Questions