Excess electrons are placed on a small lead sphere with mass 8.00 g so that its net charge is - 3.20 X 10- 9 C. (10 marks) (a) Find the number of excess electrons on the sphere. (b) How many excess electrons are there per lead atom?

1 Answer
A08
Jul 31, 2018

Charge on one electron #e = -1.60×10^-19\ C#

(a) Number of excess electrons #=(- 3.20xx 10^- 9)/(-1.60×10^-19)= 2.0×10^10#

(b) We know that Atomic mass of lead is #207.2\ "amu"#
We also know that #1#gram mole of lead will have #6.022×10^23# atoms
#:.# Number of atoms in the sphere#=8.00/207.2xx6.022×10^23#
Excess electrons per lead atom #=(2.0×10^10)/(8.00/207.2xx6.022×10^23)#

#=8.6xx10^-13#

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