When 52.1 g of calcium is reacted with nitrogen gas, 27.9 g of calcium nitride is produced. What is the percent yield of calcium nitride for this reaction?

1 Answer
Meave60
May 1, 2018

The percent yield of #"Ca"_3"N"_2"# is #"43.5%"#.

Explanation:

Start with a balanced equation.

#"3Ca(s) + N"_2("g")##rarr##"Ca"_3"N"_2"#

First you need to determine the theoretical yield of calcium nitride using stoichiometry. Once you known the theoretical yield, you can calculate the percent yield.

Theoretical Yield

  1. Calculate mole #"Ca"# by dividing the given mass by its molar mass (atomic weight in g/mol). Since molar mass is a fraction, I prefer to divide by multiplying by the inverse of the molar mass, #"mol/g"#. I believe it's easier to see what happens with the units.

  2. Next determine mol #"Ca"_3"N"_2"# by multiplying mol #"Ca"# by the mol ratio between #"Ca"# and #"Ca"_3"N"_2"# from the balanced equation, with #"Ca"_3"N"_2"# in the numerator.

  3. Determine mass #"Ca"_3"N"_2"# by multiplying mol #"Ca"_3"N"_2"# by its molar mass #("148.248 g/mol")#.
    https://pubchem.ncbi.nlm.nih.gov/compound/3387080

#52.1color(red)cancel(color(black)("g Ca"))xx(1"mol Ca")/(40.078color(red)cancel(color(black)("g Ca")))="1.30 mol Ca"#

#1.30color(red)cancel(color(black)("mol Ca"))xx(1"mol Ca"_3"N"_2)/(3color(red)cancel(color(black)("mol Ca")))="0.433 mol Ca"_3"N"_2"#

#0.433color(red)cancel(color(black)("mol Ca"_3"N"_2))xx(148.248"g Ca"_3"N"_2)/(1color(red)cancel(color(black)("mol Ca"_3"N"_2)))="64.2 g Ca"_3"N"_2"# (rounded to three significant figures)

Percent Yield

#"percent yield"=abs(("actual yield")/("theoretical yield"))xx100%#

#"percent yield"=abs((27.9color(red)cancel(color(black)("g Ca"_3"N"_2)))/(64.2color(red)cancel(color(black)("g Ca"_3"N"_2"))))xx100%#

#"percent yield"##=##"43.5 %"#

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