Question #8c92c

1 Answer
May 12, 2016

The limiting reactant is "Ca"_10"F"_2("PO"_4)_6. The theoretical yield of "CaSO"_4 is 13.5 g. The percent yield of "CaSO"_4 is 290 % (pretty good!). The volume of "HF" at STP will
be 338 L.

Explanation:

Identify the limiting reactant

The balanced chemical equation is

"Ca"_10"F"_2("PO"_4)_6 + "H"_2"SO"_4 → "3Ca"_3("PO"_4)_2 + "CaSO"_4 + "2HF"

From "Ca"_10"F"_2("PO"_4)_6 :

"Moles of CaSO"_4 = 100 color(red)(cancel(color(black)("g Ca"_10"F"_2("PO"_4)_6))) × (1 color(red)(cancel(color(black)("mol Ca"_10"F"_2("PO"_4)_6))))/(1008.61 color(red)(cancel(color(black)("g Ca"_10"F"_2("PO"_4)_6)))) × ("1 mol CaSO"_4)/(1 color(red)(cancel(color(black)("mol Ca"_10"F"_2("PO"_4)_6)))) = "0.099 15 mol CaSO"_4

From "H"_2"SO"_4:

"Moles of CaSO"_4 = 0.500 color(red)(cancel(color(black)("L H"_2"SO"_4))) × (0.750 color(red)(cancel(color(black)("mol H"_2"SO"_4))))/(1 color(red)(cancel(color(black)("L H"_2"SO"_4)))) × ("1 mol CaSO"_4)/(1 color(red)(cancel(color(black)("mol H"_2"SO"_4)))) = "0.375 mol CaSO"4

"Ca"_10"F"_2("PO"_4)_6 gives fewer moles of "CaSO"_4, so "Ca"_10"F"_2("PO"_4)_6 is the limiting reactant.

Theoretical yield of "CaSO"_4

"Mass of CaSO"_4 = "0.099 15" color(red)(cancel(color(black)("mol CaSO"_4))) × ("136.2 g CaSO"_4)/(1 color(red)(cancel(color(black)("mol CaSO"_4)))) = "13.5 g CaSO"_4

Percent Yield of "CaSO"_4

"% yield" = "actual yield"/"theoretical yield" × 100 % = (39.2 color(red)(cancel(color(black)("g"))))/(13.5 color(red)(cancel(color(black)("g")))) × 100 % = 290 %

Yield of "HF"

"Moles of HF" = 7500 color(red)(cancel(color(black)("g Ca"_10"F"_2("PO"_4)_6))) × (1color(red)(cancel(color(black)( "mol Ca"_10"F"_2("PO"_4)_6))))/(1008.61 color(red)(cancel(color(black)("g Ca"_10"F"_2("PO"_4)_6)))) × "2 mol HF"/(1 color(red)(cancel(color(black)("mol Ca"_10"F"_2("PO"_4)_6)))) = "14.87 mol HF"

PV = nRT

V = (nRT)/P = (14.87 color(red)(cancel(color(black)("mol"))) × "0.083 14" color(red)(cancel(color(black)("bar")))·"L"·color(red)(cancel(color(black)("K"^"-1""mol"^"-1"))) × 273.15 color(red)(cancel(color(black)("K"))))/(1 color(red)(cancel(color(black)("bar")))) = "338 L"