Question

How much electric charge must move through a load to release 50 J of energy when potential drop across the load is 120 V.

Answer 1

Note that:
\[U=\frac{ 1 }{ 2 }QV\]
Where U is the energy in Joules given charge Q (coulombs) and V voltage in Volts.
I'll let you take it from here.

Answer 2

apply E=1\2 CV^2
Calculate value of C from Here

Answer 3

Pardon me but E=1/2CV^2 is the energy on a charged capacitor not the energy expended in dropping a charge through a potential.