Question

Crystalline $CsCl$ has density $3.988gc{m}^{-3}$. The volume occupied by single CsCl pair in the crystal will be:
(Molar mass $CsCl=168.4g/mol$ )

• A. $7.014\times 10^{-3}c{m}^3$
• B. $7.014\times 10^{-23}c{m}^3$
• C. $1.014\times 10^{-3}c{m}^3$
• D. $1.542\times 10^{-5}c{m}^3$

Answer 1

Answer: (B)

$CsCl$ forms $SCC$ lattice ($BCC$ type), $Z=1$

Volume of unit cell $=$ volume of single $CsCl$ ion pair $=a^3$

$d=\frac{Z\times M}{N_A\times a^3}$

$\Rightarrow a^3=\frac{Z\times M}{d\times N_A}$

$=\frac{1\times 168.4}{3.988\times 6.023\times 10^{23}}$

$=7.014\times 10^{-23}c{m}^3$