Question

Assume that each of copper atom has one free electron and there is $1mg$ of copper. Given that atomic weight of copper $=63.5$ and Avogadro number $=6.02\times 10^{23}.$ What is the charge possessed by these free electrons?

• A. 1.52 C
• B. 1.76 C
• C. 4.76 C
• D. 1.25 C

Answer 1

Answer: (A)

Number of atom in $1g$ of copper,
$n=\frac{\text{ Avogadro number }}{\text{ atomic weight }}=\frac{6.02\times 10^{23}}{63.5}=9.48\times 10^{21}$
Therefore, number of atoms i.,e, number of free electrons in $1mg$ of copper,
$n^{\prime }=9.48\times 10^{21}\times 10^{-3}=9.48\times 10^{18}$
Charge possessed by these free electrons,
$q=n^{\prime }e=9.48\times 10^{18}\times 1.6\times 10^{-19}=1.517C$