Question

What is the percent yield of a reaction in which 200 grams of phosphorus trichloride reacts with excess water to form 7.0 grams of HCl and aqueous phosphorus acid?

Answer 1

first write the balanced equation

PCl₃ + 3 H₂O -------> H₃PO₃ + 3 HCl

no of moles of PCl3 = weight of PCl3 / molar mass of PCl3

= 200 / 135.9

= 1.471 moles

no of moles of HCl formed = 7 / 36

= 0.194 moles

from the equation it is clear that one mole of PCl3 will give three moles of HCl

so theritically 1.471 moles should give 3 x 1.471 = 4.413 moles we should get

but we got only 0.194 moles

% yield = actual yield / theritical yoeld x 100

= 0.194 / 4.413   x 100

= 4.4 % yield