A container holds a gas consisting of 1.75 moles of oxygen molecules. One in a million of these molecules has lost a single electron. What is the net charge of the gas. 1.6 x 10^-19(C/e^-) x n(e^-) So I'm looking for the number of electrons (n) which I think is 1.05625 x 10^19 and the final answer would be .169C. "Working backwards from the answer in the back" but I do not understand how I would figure out the number of electrons. Help?