Question

Question about finding the limiting reactant. So far, I found the molar mass (g/mol) of each substance in this chemical reaction but I'm not sure what to do next.

Phosphoric acid can be prepared by reaction of sulfuric acid with “phosphate rock” according to
the equation:
Ca3(PO4)2 + 3H2SO4  3CaSO4 + 2H3PO4
Suppose the reaction is carried out starting with 129 g of Ca3(PO4)2 and 97.4 g of H2SO4. Which
substance is the limiting reactant?
A) Ca3(PO4)2
B) H2SO4
C) CaSO4
D) H3PO4
E) none of these

Answer 1

\(\bf{Step ~1}\): Use the given grams for each of the reactants and convert to moles

\(\bf{Step~ 2}\): Use those mols of each reactants and convert to mols of Phosphoric acid (H3PO4). You use mole to mole ratios:
For every 1 mole of reactant Ca3(PO4)2 , only 2 moles of H3PO4 is produced as products
For every 3 moles of reactant 3H2SO4 , only 2 moles of H3PO4 is produced as products

\(\bf{ Step ~3}\): Compare which mols of 2H3PO4 is less. The less mols of the products indicates the reactants you started with was the limiting reactant.

Answer 2

Thank you!!

Answer 3

actual yield / theoretical yield x 100
grams - moles - grams - moles

Answer 4

No problem! :)