Metallic iron crystallizes in a cubic lattice. The unit cell edge length is 287 pm. The density of iron is 7.87 g/cm3. How many iron atoms are within a unit cell?

Respuesta :

Answer: The number of iron atoms in one unit cell are 2

Explanation:

To calculate the number of iron atoms in 1 unit cell, we use the equation to calculate the density of metal, which is:

[tex]\rho=\frac{Z\times M}{N_{A}\times a^{3}}[/tex]

where,

[tex]\rho[/tex] = density  = [tex]7.87g/cm^3[/tex]

Z = number of atom in unit cell = ?

M = atomic mass of metal = 55.85 g/mol

[tex]N_{A}[/tex] = Avogadro's number = [tex]6.022\times 10^{23}[/tex]

a = edge length of unit cell = [tex]287pm=287\times 10^{-10}cm[/tex]    (Conversion factor:  [tex]1cm=10^{10}pm[/tex]  )

Putting values in above equation, we get:

[tex]7.87=\frac{Z\times 55.85}{6.022\times 10^{23}\times (287\times 10^{-10})^3}\\\\Z=\frac{7.87\times 6.022\times 10^{23}\times (287\times 10^{-10})^3}{55.85}=2[/tex]

Hence, the number of iron atoms in one unit cell are 2

"2" iron atoms are within a unit cell.

According to the question,

  • Density, [tex]\rho = 7.87 \ g/cm^3[/tex]
  • Atomic mass, [tex]M = 55.85 \ g/mol[/tex]
  • Avogadro's number, [tex]N_A = 6.022\times 10^{23}[/tex]
  • Edge length, [tex]a = 287 \ pm \ or \ 287\times 10^{-10} \ cm[/tex]

We know,

→ [tex]\rho = \frac{Z\times M}{N_A\times a^3}[/tex]

By putting the values,

[tex]7.87 = \frac{Z\times 55.85}{6.022\times 10^{23}\times (287\times 10^{-10})^3}[/tex]

  [tex]Z = \frac{7.87\times 6.022\times 10^{23}\times (287\times 10^{-10})^3}{55.85}[/tex]

     [tex]= 2[/tex]

Thus the solution above is right.  

Learn more about unit cell here:

https://brainly.com/question/14272012