Identify the 'A' in the following reaction.
$\text{CaC}_2 + \text{H}_2\text{O} \rightarrow \text{A} + \text{Ca(OH)}_2$

Calculate the number of atoms in 1 g metal that forms bcc crystal structure $[\rho \times a^3 = 6 \cdot 6 \times 10^{-22} \text{ g}]$

Which of the following dopants is used in germanium to form n-type semiconductor ?

Calculate the void volume of bcc unit cell if volume of unit cell is $8 \cdot 0 \times 10^{-23} \text{ cm}^3$