physics: coulumb's law and superposition?

Question

3) Styrofoam is a polymer containing carbon and hydrogen. Assume the formula is C8H8. How many molecules are in a 0.2 g styrofoam peanut? How many protons and electrons are in this peanut if it carries no excess charges? How many coulombs of positive and negative charge does this represent? If the peanut has an excess charge of 0.05C, how many of its electrons has it gained or lost?

Answer 1

First how many molecules are contained per gram of Styrofoam. Thank to a good friend of my Amedeo Avogadro (Sh... he likes to called Count ) has come up with a a remarkable idea that 1 mole of matter contains 6.022 E+23 atoms per mole.

So how many moles there are in 0.2g of Styrofoam?
we have C8H8 and that means (looking at the periodic table) that 1 mole of C8H8 =8( 12.0107 )+8( 1.0079)= 104.15g / mole
so 0.2 g = 0.00192moles so let m=0.00192moles
So # of molecules = Nm=11.56 E+20

Now since 1 mole has protons and nummber of protons = number of electrons we have
#e- = #e+ = 8(6)+ 8(1)=56 protons or electrons per mole

does that help?