The reaction of 4.210 g of salicylic acid (#"C"_7"H"_6"O"_3#) with 15.0 mL of acetic anhydride (#"C"_4"H"_6"O"_3; ρ = "1.082 g/mL"#) yields 3.92 g of aspirin (#"C"_9"H"_8"O"_4#). What are the theoretical and percentage yields of aspirin?

Question

Wyatt Adkins · Accepted Answer

WARNING! Long answer! The theoretical yield is 5.493 g; the percent yield is 71.4 %.

The limiting reactant must be found before the theoretical and percentage yields can be determined. Let's start by creating a balanced equation that includes the masses, moles, and molar masses of the compounds in question since we know we will need it. Determine which reactant is limiting. Molar masses should be placed above the formulas and everything else should be placed below them. Compile all the data in one location. #M_text(r):color(white)(mmmll)138.1color(white)(mmmm)102.1color(white)(mmmm)180.2# #color(white)(mmmmm)underbrace("C"_7"H"_6"O"_3)_color(red)("salicylic acid") + underbrace("C"_4"H"_6"O"_3)_color(red)("acetic anhydride") → underbrace("C"_9"H"_8"O"_4)_color(red)("aspirin") + underbrace("C"_2"H"_4"O"_2)_color(red)("acetic acid")# #color(white)(mmmmmmm)"A"color(white)(mll) +color(white)(mml) "B"color(white)(mml) →color(white)(mll) "C"color(white)(mll) +color(white)(ml) "D"# #"Mass/g:"color(white)(mm)4.210color(white)(mmmm)16.23# #"Mmol:"color(white)(mml)30.485color(white)(mmmm)159.0# #"Divide by:"color(white)(mm)1color(white)(mmmmmm)1# #"Mmol rxn:"color(white)(l)30.485color(white)(mmmm)159.0# #"Moles of A" = 4.210 cancel("g A") × "1 mol A"/(138.1 cancel("g A")) = "0.030 485 mol A" = "30.485 mmol rxn"# #"Mass of B" = 15.0 color(red)(cancel(color(black)("mL B"))) × "1.082 g B"/(1 color(red)(cancel(color(black)("mL B")))) = "16.23 g B"# #"Moles of B" = 16.23 color(red)(cancel(color(black)("g B"))) × "1 mol B"/(102.1 color(red)(cancel(color(black)("g B")))) = "0.1590 mol B" = "159.0 mmol B"# #"A"# gives the fewer moles of reaction, so #"A"# is the limiting reactant. Determine the theoretical yield. #"0.030 485" cancel("mol A") × (1 color(red)(cancel(color(black)("mol C"))))/(1 color(red)(cancel(color(black)("mol A")))) × "180.2 g C"/(1 cancel("mol C")) = "5.493 g C"# Determine the yield percentage. #"% yield" = "actual yield"/"theoretical yield" × 100 % = (3.92 color(red)(cancel(color(black)("g"))))/(5.493 color(red)(cancel(color(black)("g")))) × 100 % = 71.4 %#

Ellie Andrews · Answer

undefined Theoretical yield of aspirin: 5.44 g
Percentage yield of aspirin: 72%