An object has a static charge of -2x10-^10 C How many excess electrons have been trandferred to it?

1 C = 6.242 * 10^18 charges


so,


excess charges = -2*10^-10 * 6.242 * 10^18 = -1.25 * 10^9


i.e. about 1.25 * 10^9 electrons.