What is the theoretical yield of Li3N in grams when 12.3 g of Li is heated with 33.6g of N2?if the actual yield of Li3N is 5.89g,what is the percent yield of thereaction?
Answer:
In order to determine the theoretical yield, we must first find the limiting reactant (reagent), which will determine the greatest possible amount of product that can be produced.
Molar Masses
Li:6.941 g/mol
N2:(2×14.007g/mol)=28.014 g/mol
Li3N:(3×6.941g/mol Li)+(1×14.007g/mol N)=34.83 g/mol Li3N
Limiting Reactant
Divide the mass of each reactant by its molar mass, then multiply times the mole ratio from the balanced equation with the product on top and the reactant on bottom, then multiply times the molar mass of Li3N.
Lithium
12.5g Li×1mol Li6.941g Li×2mol Li3N6mol Li×34.83g Li3N1mol Li3N=20.9 g
Li3N
Nitrogen Gas
34.1g N2×1mol N228.014g N2×2mol Li3N1mol N2×34.83g
Li3N1mol Li3N=84.8 g Li3N
Lithium produces less lithium nitride than nitrogen gas. Therefore, the limiting reactant is lithium, and the theoretical yield of lithium nitride is 20.9 g.
percent yield
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