Question

What is percentage composition of element by mass in the lithium nitride salt, `Li_3N`?

Answer 1

The metal has approx. `60%` composition by mass with respect to lithium..

Explanation:

`"% composition by mass"="mass of component"/"molar mass of compound"xx100%`.

And thus `%Li=(3xx6.941*g*mol^-1)/(34.83*g*mol^-1)xx100%=??%`.

Answer 2

The mass percentage of `Li` in `Li_3N` is `59.7%`

Explanation:

The obtain the mass percentage of `Li` in `Li_3N`, we first calculate the total mass of `Li_3N`. This can be done by adding up the masses:

mass `Li`=6.9u
mass `N`=14.0u
Therefore the mass of `Li_3N` is 3 times the mass of `Li` and 1 time the mass of `N` added up together:

`3xx6.9+1xx14.0=34.7 u`

Now to obtain the mass percentage of `Li` in this compound we have to divide the mass of three times `Li` by the mass of `Li_3N`.

`(3xx6.9)/34.7xx100%=59.7%`

Answer 3

`"Li" = 59.8%`

`"N" = 40.2%`

Explanation:

Find the mass of 3 atoms of lithium:

`3"Li" * 6.941 color(white)".""amu" = 20.823 color(white)".""amu"`

Find the mass of 1 atom of nitrogen:

`1 "N" * 14.0067 color(white)".""amu" = 14.0067 color(white)".""amu"`

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Now use the formula:

`% "mass" = "part"/"whole"times100%`

For Lithium:

`%"Li" = 20.823/(20.823+14.0067) = 59.8%`

For Nitrogen:

`%"N" = 14.0067 / (20.823+14.0067) = 40.2%`

Final Answer