The density of copper is `9xx10^3 kg m^(-3)` and its atomic mass is 63.5 u. Each copper atom provides one free electron. Estimate the number of free electrons per cubic metre in copper.

Options

A. `10^(19)`
B. `10^(23)`
C. `10^(25)`
D. `10^(29)`

Answer

D

Explanation

Here,
Density of copper, `rho=9xx10^(3)kgm^(-3)=9xx10^(6)gm^(-3)`
Avogadro number, `N_(A)=6.02xx10^(23)`
Mass of 1 mole of copper atoms, `M=63.5 g`
As each copper atom contributes one free electron.
Therefore, number of free electrons per unit volume is
`n=(N_(A))/(M)rho=(6.02xx10^(23))/(63.5)xx9xx10^(6)=0.85xx10^(29)m^(-3)`