How many coulombs of charge do 50 * 10^31 electrons possess

Quantity of Charge , Q = ne
Where n = number of electrons
             e = charge on one electron = -1.6 * 10 ^-19  C.
             n = 50 * 10^31  electrons

Q =    (50 * 10^31)*( -1.6 * 10 ^-19 ) =  -8 * 10^13 C.

Note that the minus sign indicates that the charge is a negative charge.

Ithink it’s cancer risk

This is what a calorimeter is used for simpler ex, to measure calories in food.