We're told that the fundamental charge of an electron is -1.60×10-19 Coulombs. If a scientist determines the charge to mass ratio of an electron is -1.76×108 Coulombs/gram, what will be the total mass of an electron?
All right, so for a question like this, they want us to determine the total Max. So that is what our end amount needs to be. So end amount here will be the grams of our electrons and our given amount. Remember our given amount is when we have a value that has only one unit connected to it and here that one unit by itself would be this charge of an electron. So that's our given amount 1.60×10-19 coulombs. Remember, don't forget the negative sign.
Now to go from the given amount to the end amount, we have to utilize conversion factors. Remember, conversion factor is when you have two units tied together. Our conversion factor here would be -1.76×108 coulombs/gram. Coulombs and grams are two different units that are being tied together. We need to cancel out Coulombs. So we put the -1.76×108 Coulombs on the bottom and that's for everyone Gram. So this would represent our conversion factor, and we'd see here that Coulombs would cancel out and have as my units at the end grams, which is what I'm looking for.
So all we have to say here is this question requires only one conversion factor. So then it's just going to be this value here divided by this value here and that'll give us our grams. Remember, when you have a number written in scientific notation, you need to put it in parentheses, otherwise you may get the incorrect answer. If you do this correctly, you'll get approximately 9.10×10-28 g as the total mass of your electron. So based on that answer, option B would be the correct choice.