Question

Estimate charge on all the electrons in a 10g cu penny.

Answer 1

The total number of electrons in an atom of Cu is 29 
Given,
mass=10g

Molar mass= 63.5 
Therefore,
no. of moles of Cu = 10/63.5 = 0.157
So,
total numbers of electron =0.157*6.023*1023*29 =N(let).
So,

the toal charge due to N electrons is 
Qe = N*e { e is the fundamental charge =1.6*10-19} 
     = 0.157*6.023*1023*29*1.6*10-19 
     = 4.387*105 C