Q8 / 150 · MHT CET 2023 (12 May Shift 1) · Chemistry

Calculate the molar mass of an element having density $7.8 \mathrm{~g} \mathrm{~cm}^{-3}$ that forms bec unit cell. $\left[\mathrm{a}^3 \cdot \mathrm{N}_{\mathrm{A}}=16.2 \mathrm{~cm}^3 \mathrm{~mol}^{-1}\right]$

  • Correct answer
    A
    $63.18 \mathrm{~g} \mathrm{~mol}^{-1}$
  • B
    $61.23 \mathrm{~g} \mathrm{~mol}^{-1}$
  • C
    $59.31 \mathrm{~g} \mathrm{~mol}^{-1}$
  • D
    $65.61 \mathrm{~g} \mathrm{~mol}^{-1}$

Solution

For bec unit cell, $\mathrm{n}=2$. $$ \begin{aligned} & \text { Density }(\rho)=\frac{\mathrm{Mn}}{\mathrm{a}^3 \mathrm{~N}_{\mathrm{A}}} \\ & 7.8=\frac{\mathrm{M} \times 2}{16.2} \\ & \mathrm{M}=\frac{7.8 \times 16.2}{2}=63.18 \mathrm{~g} \mathrm{~mol}^{-1} \end{aligned} $$

Hence, the correct answer is option: 'A'.

Relevant Questions