Question

What is the total positive charge in a solid copper penny that is electrically neutral?

Answer 1

Explanation:

Let us assume that the given mass (m) is 3.1 grams.

Also, we assume that the given penny is entirely made up of copper. Therefore, the number of moles (n) of this copper penny are as follows.

              No. of moles = \frac{mass}{\text{M olar mass}}[/tex]

Now, multiply by Avogadro's number ($N_A$) to get total number of atoms:

                N = $n \times N_A$

or,             N = $N_A \times \frac{mass}{\text{M olar mass}}$

Now, multiply by the atomic number Z of copper. This is the number of protons per atom by definition.

      $N_protons = Z \times N_A {mass}{\text{M olar mass}}$

Let us now multiply by e, the elementary charge, which is the charge of each proton:

        $q_protons = Z \times e \times N_A \times {mass}{\text{M olar mass}}$

           = $29 \times 1.6 \times 10^{-19} \times 6.022 \times 10^{23} \times \frac{0.0031}{63.546}$

           = 136.3 C

Now, negate to get charge of electrons:

      $q_electrons = -q_protons$

                     = -136.3 C

Thus, we can conclude that the total positive charge in a solid copper penny that is electrically neutral is 136.3 C .