Question

A system consists of electrons and protons only. It contains 150 electrons and has a total charge of +22e. What is the mass of the system? me=9.11 x 10^â31kg, mp=1.673 x 10^â27kg.

Answer 1

According to the statements the number of electrons is 150, then

e = 150

But there is a positive charge of +22e, then the number of protons would be

p = 150+172

If the mass of the electrons is

$m_e = 9.11*10^{-31} kg$

And the mass of the protong is

$m_p = 1.673*10^{-27}kg$

We have that the total mass of the system would be

$m = e*m_e +pm_p$

$m = 150 * (9.11*10^{-31})+170(1.673*10^{-27})$

$m = 2.84547*10^{-25} kg$