# The compound CuCl has FCC structure like ZnS. Its density is 3.4 g cm-3. What is the length of the edge of the unit cell?

**The compound CuCl has FCC structure like ZnS. Its density is 3.4 g cm ^{-3}. What is the length of the edge of the unit cell?**

**Answer:**

**Given Values**

Density = 3.4 gm/cm^{3}

Formula mass (M) = CuCl = 63.5+35.5=99

CuCl has FCC unit cell. So, Z = 4

Avogadro Number (N_{A}) = 6.02 × 10^{23}

Formula used : \( D=\frac{Z \times M}{\left ( a \right )^{3}\times N_{A}} \)

**Calculations**

Let us find the edge length (a) using the density of the unit cell

\( \left ( a \right )^{3}=\frac{Z \times M}{D \times N_{A}} \)

\( \left ( a \right )^{3}=\frac{4 \times 99}{3.4 \times 6.02 \times 10^{23}} \) = 193.45 × 10^{-24} cm^{3}

a = 5.783 × 10^{-8} cm = 578.3 pm

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