Question

Calculate the total positive or negative charge on a $2.35g$ copper penny. Given Avogadro number $=6.02\times {10}^{23}$, atomic number of copper $=29$ and atomic mass of copper $=63.5$

Answer 1

Given mass of copper penny $=2.35g$

Atomic mass of copper $=63.5g$

Avogadro number $=6.02\times {10}^{23}$

Atomic number of copper $=29$

We have to find the positive or negative charges on $2.35$ of copper.

First, we find the total number of atoms in $2.35g$ of copper.

$=\frac{2.35}{63.5}\times 6.02\times {10}^{23}$

$=0.22\times {10}^{23}$ atoms

Since one atom of copper contains $29$ electrons (and $29$ protons).

So, $0.22\times {10}^{23}$ atoms contain $=29\times 0.22\times {10}^{23}$ electrons or protons.

So total positive/negative charges in $2.35g$ of copper is $=29\times 0.22\times {10}^{23}\times 1.6\times {10}^{-19}C$

$=10.208\times {10}^{4}C$

and equal amount of negative charge ($-10.208\times {10}^{4}C$)

where $1.6\times {10}^{-19}$ is charge on proton/electron.