Question

Calculate the total positive or negative charge on a $3.11g$ copper penny. Given Avogadro number $ = 6.02 \times {10^{23}}$, atomic number of copper $ = 29$ and atomic mass of copper $ = 63.5$
A. $3.37 \times {10^5}C$
B. $2.37 \times {10^5}C$
C. $1.37 \times {10^5}C$
D. $0.37 \times {10^5}C$

Answer 1

Hint:In order to solve this question you have to find the total positive or negative charge on a $3.11g$ copper penny. Firstly, you have to calculate the total number of atoms in the given amount of copper.

Complete step by step solution:
It is given in the question that the mass of the copper penny $ = 3.11g$
The atomic number of the copper is also given $ = 29$
And the atomic mass of the copper $ = 63.5$
We know that the Avogadro number $ = 6.02 \times {10^{23}}$
In this question you have to calculate the total positive or negative charge on a $3.11g$ copper penny.
In order to do so, firstly you have to calculate the total number of atoms in $3.11g$ of copper, which is given by,
We know that the total number of atoms in $63.5g$ of copper $ = 6.02 \times {10^{23}}$
Hence, total number of atoms in $3.11g$ of copper $ = \dfrac{{3.11}}{{63.5}} \times 6.02 \times {10^{23}}$

$ = 0.295 \times {10^{23}}$

Since, we know one atom of copper contains $ = 29$ electrons or protons.
So, $0.295 \times {10^{23}}$ atoms contain $ = 29 \times 0.295 \times {10^{23}}$ electrons or protons.
As we also know that the charge on one electron or proton $ = 1.6 \times {10^{ - 19}}C$
the total positive or negative charge on a the given amount of copper $ = 29 \times 0.295 \times {10^{23}} \times 1.6 \times {10^{ - 19}}C$

$ = 1.368 \times {10^5}C$

So, the total positive or negative charge on a $3.11g$ copper penny is $1.37 \times {10^5}C$ approx.
Therefore, the correct option is (C).

Note:Always remember that the Avogadro’s number is defined as the number of units in one mole of any substance. It is the proportionality factor and is related to the number of constituent particles in a sample with the amount of substance in that sample. Also remember that the amount of charge on one electron and proton is the same in magnitude.