Question

a) Copper crystallizes into a fcc lattice with edge length $3.61\times {10}^{-8}$. Show that the calculated density is in agreement with its measured value of $8.92g/c{m}^3$
b) Which type of forces are present in ionic solids?

Answer 1

(a) Given that

Length of edge $\left(a\right)=3.61\times {10}^{-8}cm$

Atomic mass of cupper $\left(M\right)=63.55g/mol$

Avogadro constant $\left(N_A\right)=6.023\times {10}^{23}$ per mole

Number of atoms in unit cell of FCC$\left(Z\right)=4$

As we know that density $\left(d\right)$ is given as-

$d=\frac{ZM}{a^3{N}_A}$

$\Rightarrow d=\frac{4\times 63.5}{{(3.61\times {10}^{-8})}^3\times 6.023\times {10}^{23}}$

$\Rightarrow d=\frac{254}{47.04\times {10}^{-24}\times 6.023\times {10}^{23}}$

$\Rightarrow d=8.92g/{cm}^3$

Hence the density is $8.92g/{cm}^3$.

(b) An ionic bond is the electrostatic force of attraction between two oppositely charged ions. Hence electrostatic force is present in ionic solids.