Final answer:
When spheres A and B are touched together and then separated, they will both end up with a charge of -4.0 µC. Sphere C, with a charge of +4.0 µC, will have an excess of 2.5 x 10^13 electrons.
Step-by-step explanation:
When sphere A and B are touched together and then separated, they will end up with an equal and opposite charge. Since sphere A has a charge of -2.0 µC and sphere B has a charge of -6.0 µC, they will both end up with a charge of -4.0 µC. This means that sphere C, which carries a charge of +4.0 µC, will end up with an excess of electrons. To determine the number of excess electrons, we can use the relationship Q = ne, where Q is the charge in coulombs, n is the number of excess or deficient particles (electrons or protons), and e is the elementary charge, which is 1.6 x 10^(-19) coulombs. Rearranging the equation, we can solve for n, which gives us n = Q/e. Plugging in the values, we find n = (4.0 x 10^(-6) C) / (1.6 x 10^(-19) C/particle) = 2.5 x 10^13 electrons. Therefore, sphere C will end up with an excess of 2.5 x 10^13 electrons.