Question

3 C2H5OH + PCl3 → 3 C2H5Cl + H3PO3 If a chemist starts with 105.0 g of ethanol and 135.65 g of phosphorus trichloride, then what is the limiting reagent?

Answer 1

according to above equation

3mole of C2H5OH react with 1 mole of
PCl3.

hence 46x3=138g of C2H5OH react with 137.5 g of PCl3

hence 1 g of C2H5OH react with 137.5/138g PCl3

hence 105 g of C2H5OH react with (137.5/138) x 105 g of PCl3

but PCl3 given 135.65g which is greater then (137.5/138) x 105 g
it means C2H5OH is not enough to continue reaction hence C2H5OH is limiting reagent.