For the following consider that the charge of an electron is 1.6x10^-19 C and Av
ID: 1307574 • Letter: F
Question
For the following consider that the charge of an electron is 1.6x10^-19 C and Avogadro's number is 6.022x10^23 atoms/mol and one mole of aluminum has a mass of 27 grams and aluminum has an atomic number of 13. Imagine that you have a 0.1 kg sphere of aluminum.
a. How many atoms are there in that aluminum?
b. How many electrons are in the piece of aluminum if it were neutral?
NOW imagine that the aluminum jas a charge of +5uC (u is 10^-6)
c. Is there an excess or deficiency of electrons on the aluminum? How do you know?
d. How many electrons were removed or added to the aluminum sphere?
e. What fraction of the total electrons were added or removed?
f. Is this fraction significant? What might your answer imply about the avaliability of charge around us?
g. What would happen of you brought your +5uC charged aluminum sphere into contact with a copper sphere of the same demensions and then seperated them? Explain your reasoning.
h. If I brought a third similarly sized neutral sphere into contact with the copper sphere (after it was seperated from the original sphere) and then seperated them, what would the charge be on the three spheres?
Explanation / Answer
1)number of atoms=number of moles*avogadro's number
=(100/27)*6.923*10^23
=2.23*10^24 atoms.
b)number of electrons if if were neutral=2.23*10^24*13
=2.9*10^25 electrons
c)there is a deficiency of electrons since protons cannot be removed from the molecule
d)number of electrons=5*10^-6/(1.6*10^-19)
=3.125*10^13 electrons
e)fraction of electrons removed=3.125*10^13/2.9*10^25
=1.077*10^-12
f)no this fraction is insignificant on part of alumnum.
g)electrons would flow from the copper sphere to the aluminum sphere until both have equal potential.
h)charge of aluminum=5/2
=+2.5 uC
charge on copper=5/4
=+1.25 uC
charge on third sphere=5/4
=+1.25 uC