A 20 mm diameter copper ball is charged to 44 nC What fracti

A 2.0 mm diameter copper ball is charged to +44 nC. What fraction of its electrons have been removed? The density of copper is 8,920 kg/m³.

radius = 1 mm = 10^-3 m

volume of copper ball = v = (4/3)*pi*r^3

mass of the copper ball , m = D*v = D*(4/3)*pi*r^3

molar weight of copper = 0.063546 kg/mol

number of moles = m/M

number of atoms = m*N/M

N = avagadro number = 6.023*10^23

number of electrons = Z*m*N/M = (29*8920*(4/3)*pi*10^-9*6.023*10^23)/(0.063546)

total number of electrons = 1.027*10^22

charge on the sphere = Q = +44 nC

but Q = n*e

number of electrons removed n = Q/e = (44*10^-9)/(1.6*10^-19) = 2.75*10^11

fraction = 2.75*10^11/(1.027*10^22)

fraction = 2.68*10^-11