Question

A system of 1520 particles, each of which is either an electron or a proton, has a net charge of −6.784×10−17 C .

How many electrons are in this system?

What is the mass of this system?

Thank you in advance

Answer 1

a) the net charge on the system =-6.784*10^-17C

since electron is negatively charged we have=-6.784*10^-17/-1.6*10^-19c=424 more eletrons

so we can see the number of electrons is higher, so the exact number of protons is=1520-424/2=548

so exact number of electrons=1520-548=972

so the answer is 972 electrons

b) the mass of the system

n1*mass of electron+n2*mass of proton

972*9.11*10^-31kg+548 *1.67*10^-27kg=9.17*10^-25kg

so the answer is 9.17*10^-25kg or 9.20*10^-25kg