$A$ compound has $fcc$ structure. If the density of the unit cell is $3.4 \text{ g cm}^{-3}$,what is the edge length of the unit cell? (Molar mass $= 98.99 \text{ g mol}^{-1}$)

$KCl$ has the same structure as $NaCl$. If ${r_{Na^+}}/{r_{Cl^-}} = 0.55$ and ${r_{Na^+}}/{r_{K^+}} = 0.74$,then the ratio of the edge lengths of $KCl$ and $NaCl$ is:

Calculate the number of unit cells in $1 \ cm^3$ of an element if the unit cell edge length is $2.0 \times 10^{-8} \ cm$.

Copper crystallises in a $ccp$ arrangement and the accepted value of the metal ion radius was found to be $1.28 \ \mathring{A}$. Calculate the density of copper in grams per cubic centimetre. (Atomic weight of copper is $63.5 \ g/mol$,$N_A = 6.022 \times 10^{23} \ mol^{-1}$) (in $g/cm^3$)

Copper crystallises in $fcc$ unit cell with cell edge length of $3.608 \times 10^{-8} \, cm$. The density of copper is $8.92 \, g \, cm^{-3}$. Calculate the atomic mass of copper. (In $u$)

Which of the following expressions is correct in the case of a $CsCl$ unit cell (edge length,$a$)?