Question

What is the mass of `"0.1 mols"` of electrons in `"amu"`?

Answer 1

Well, one electron has a rest mass of approximately:

`m_e = 9.109 xx 10^(-31) "kg"`

So for `0.1` mols of electrons...

`=> 0.1 cancel"mols" xx (N_A " things")/(cancel"1 mol") xx m_e`

`= 0.1N_Am_e`,

where `N_A = 6.0221413 xx 10^(23)` `"mol"^(-1)` is Avogadro's number.

So, the molar mass in `"g/mol"` would be:

`m_("0.1 mol" xx e) = 0.1 cdot 6.0221413 xx 10^(23) "mol"^(-1) cdot 9.109 xx 10^(-31) "kg"`

`= 5.486 xx 10^(-8) "kg/mol" = 5.486 xx 10^(-5) "g/mol"`

Recall that `"1 amu"` is numerically equal to `"1 g/mol"`. So,

`m_("0.1 mols e"^(-)) = color(blue)(5.486 xx 10^(-5) "amu")`