Question

A regular cube of metal measures exactly $10$ cm on an edge and has density $8$ g cm${}^{-3}$. If the cube contains $6\times {10}^{25}$ atoms of the metal, determine atomic weight (in g mol${}^{-1}$) of metal?

[Use $N_A=6\times {10}^{23}$]

• A. $40$
• B. $60$
• C. $80$
• D. $100$

Answer 1

The correct option is C $80$

$density=\frac{mass}{volume}$
$8=\frac{6\times {10}^{25}\times \frac{M}{6\times {10}^{23}}}{1000}$
$M=80$