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

3 Answers
May 25, 2017

Answer:

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

Answer:

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%#

May 25, 2017

Answer:

#"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