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

May 25, 2017

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%=??%.

May 25, 2017

The mass percentage of $L i$ in $L {i}_{3} N$ is 59.7%

#### Explanation:

The obtain the mass percentage of $L i$ in $L {i}_{3} N$, we first calculate the total mass of $L {i}_{3} N$. This can be done by adding up the masses:

mass $L i$=6.9u
mass $N$=14.0u
Therefore the mass of $L {i}_{3} N$ is 3 times the mass of $L i$ and 1 time the mass of $N$ added up together:

$3 \times 6.9 + 1 \times 14.0 = 34.7 u$

Now to obtain the mass percentage of $L i$ in this compound we have to divide the mass of three times $L i$ by the mass of $L {i}_{3} N$.

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

May 25, 2017

"Li" = 59.8%

"N" = 40.2%

#### Explanation:

Find the mass of 3 atoms of lithium:

$3 \text{Li" * 6.941 color(white)".""amu" = 20.823 color(white)".""amu}$

Find the mass of 1 atom of nitrogen:

$1 \text{N" * 14.0067 color(white)".""amu" = 14.0067 color(white)".""amu}$

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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%