# NEET Chemistry The Solid State Questions Solved

BOARD

An element crystallizes in a structure having fcc unit cell of an edge 200 pm. Calculate the density if 200 g of this element contains 24$×$1023 atoms.

24$×$1023 atoms of an element have mass = 200 g

$\therefore$ 6.022$×$1023 atoms of an element have mass =

$\frac{200}{24×{10}^{23}}$ $×$ 6.022 $×$1023 = 50.18 g

Given : a = 200 $\rho$m = 200$×$10-12 cm,

Z = 4(For fcc), M = 50.18 g

Using the formula : $\rho$ = $\frac{Z×M}{{a}^{3}×{N}_{A}}$

$⇒$ $\rho$ = $\frac{4×50.18}{\left(200×{10}^{-10}{\right)}^{3}×6.022×{10}^{23}}$

$\therefore$ $\rho$ = $\frac{200.72}{8×6.022×{10}^{-1}}$ = $\frac{2007.2}{48.176}$ = 41.66 g/cm3

Difficulty Level:

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