Question

Avogadro's number $=6.01\times {10}^{23}$ for the following data :
Density of NaCl = $2.165$ cm${}^{-3}$
Distance in pm between $N{a}^{+}$ and $C{l}^{-}$ in $NaCl$ is:

• A. 562
• B. 281
• C. 140.5
• D. 28.1

Answer 1

The correct option is B 281

The expression for density is given below:

$\text{Density}=d=\frac{Z\times M}{a^3\times N_a}$

$a^3=\frac{Z\times M}{N_0\times d}$ $=\frac{4\times 58.5}{6.01\times {10}^{23}\times 2.165}$ $=179.8\times {10}^{-24}$
$a=5.64\times {10}^{-8}$ cm $=564$ pm
The distance between $N{a}^{+}$ and $C{l}^{-}$ in NaCl $=\frac{a}{2}=\frac{564}{2}=281$ pm