posted by Anonymous .
Ca3(PO4)2 + 3 H2SO4 -> 3 CaSO4 + 2 H3PO4
What masses of calcium sulfate and phosphoric acid can be produced from the reaction of 1.0 kg calcium phosphate with 1.0 kg concentrated sulfuric acid (98% H2SO4 by mass)?
This is a limiting reagent problem.
1. You have the equation.
2a. Convert 1 kg calcium phosphate to moles. moles = grams/molar mass.
2b. Convert 1 kg H2SO4 to moles. Same process BUT you are starting with 1,000 x 0.98 grams and not 1 kg.
3a. Using the coefficients in the balanced equation, convert moles Ca3(PO4)2 to moles CaSO4.
3b. Use the same process to convert moles H2SO4 to moles CaSO4.
3c. It is quite likely that the answers for 3a and 3b will not be the same which means one of them must be wrong. The correct answer, in limiting reagent problems, is ALWAYS the smaller value and the reactant producing the smaller value is the limiting reagent.
4. Now convert moles CaSO4 to grams. g = moles x molar mass.
5. Repeat steps 2a, 2b, 3a, 3b, 3c, and 4 for H3PO4. A shorter way is to recognize the limiting reagent from the first part of the problem with CaSO4 and applying that information to the determination of the grams H3PO4.
Ca(OCl)2 + H3PO4