# Question 72d3b

Jun 9, 2017

$5 \cdot {10}^{- 4}$ $\text{g}$

#### Explanation:

In order to figure out the mass of $1$ mole of electrons, you need to know the mass of a single electron.

You will find it listed as

${m}_{{\text{e}}^{-}} \approx 9.10938 \cdot {10}^{- 28}$ $\text{g}$

https://en.wikipedia.org/wiki/Electron_rest_mass

Now, $1$ mole of electrons is defined as a very, very large collection that consists of $6.022 \cdot {10}^{23}$ electrons. This value, which represents the definition of a mole, is called Avogadro's constant.

So, you know the mass of single electron and the total number of electrons needed to make $1$ mole, so plug in your values and do the calculations

6.022 * 10^(23) color(red)(cancel(color(black)("e"^(-)))) * (9.109383 * 10^(-28)color(white)(.)"g")/(1color(red)(cancel(color(black)("e"^(-))))) = 5.486 * 10^(-4)# $\text{g}$

Rounded to one significant figure, the answer will be

$\textcolor{\mathrm{da} r k g r e e n}{\underline{\textcolor{b l a c k}{\text{mass of 1 mole e"^(-) = 5 * 10^(-4)color(white)(.)"g}}}}$