Question

What is the total charge of 100kg of electrons?

Answer 1

The following amount of electrons is contained in the mass of $m = 100kg$:

$$N = \dfrac{m}{m_e}$$

where $m_e = 9.11\times10^{-31}kg$ is the mass of one electron. The charge that is carried by this number of electrons is given as follows:

$$q = Ne = \dfrac{me}{m_e}$$

where $e = -1.6\times 10^{-19}C$ is the charge of one electron. Thus, obtain:

$$q = \dfrac{100\cdot (-1.6\times 10^{-19}) }{ 9.11\times10^{-31}} \approx -1.76\times10^{13}C$$

Answer. $-1.76\times10^{13}C$.