Question

Calculate the value of Avogadro's number from the following data:

Density of NaCl is $2.165$ g cm${}^{-3}$ and distance between $N{a}^{+}$and $C{l}^{-}$ in NaCl is $281$ pm.

• A. $6.01\times {10}^{21}$
• B. $6.01\times {10}^{-23}$
• C. $6.01\times {10}^{23}$
• D. None of the above

Answer 1

The correct option is C $6.01\times {10}^{23}$

For NaCl lattice,
$a=2(r^{+}+r^{-})=2\times 281=562$ pm
$d=\frac{zM}{N_A\times V}$
z is 4 because only 4 $NaCl$ are present in a unit cell
$2.165=\frac{4\times 58.5}{N_A\times (562\times {10}^{-10}{)}^3}$
$N_A=6.01\times {10}^{23}$