Copper crystallizes in a face-centered cubic lattice (the Cu atoms are at the lattice points and at the face centers). If the density of the metal is 8.96 g/cm3, what is the unit cell edge length in pm? × 10 pm

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Answer:

The unit cell edge lenght in pm is equal to 361 pm

Explanation:

Data provided:

ρ=Copper density=8.96 g/cm3

Atomic mass of copper=63.54 g/mol

Atoms/cell=4 atoms (in theory)

Avogadro's number=6.02x[tex]10^{23}[/tex] atoms/mol

Since copper has a cubic structure, its cell volume is equal to [tex]a^{3}[/tex], which can be obtained through the relationship:

cell volume=[tex]\frac{(atoms/cell)(atomic mass)}{(density)(Avogadros number)}[/tex]

Substituting the values:

cell volume=[tex]\frac{(4 atoms)(63.54 g/mol)}{(8.96 g/cm3)(6.02x10^{23}) }=4.71x10^{-23}cm^{3}[/tex]

clearing, we have:

a=[tex]\sqrt[3]{4.71x10^{-23}cm^{3} }=3.61x10^{-8}cm[/tex]

We convert from centimeter to picometer, 1cm=1x[tex]10^{10}[/tex]pm

a=[tex]3.61x10^{-8}cmx\frac{1x10^{10}pm }{1cm} =361 pm[/tex]

The unit cell edge length will be "361 pm".

Given:

Density of copper,

  • [tex]\rho = 8.96 \ g/cm^3[/tex]

Atomic mass,

  • [tex]63.54 \ g/mol[/tex]

Atoms/cell,

  • [tex]4 \ atoms[/tex]

Avogadro's number,

  • [tex]6.02\times 10^{23} \ atms/mol[/tex]

As we know the formula,

→ [tex]Cell \ volume = \frac{(Atoms/cel) (Atomic \ mass)}{(Density)(Avogadro's \ number)}[/tex]

By substituting the values, we get

→                      [tex]= \frac{4\times 63.54}{8.96\times 6.02\times 10^{23}}[/tex]

→                      [tex]= 4.71\times 10^{-23} \ cm^3[/tex]

Now,

→ [tex]a = \sqrt[3]{4.71\times 10^{-23}}[/tex]

     [tex]= 3.61\times 10^{-8} \ cm[/tex]

or,

     [tex]=361 \ pm[/tex]

Thus the above answer is correct.  

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