Question

What is the percent yield of a reaction in which 220 g of phosphorus trichloride reacts with excess water to form 122 g of HCl and aqueous phosphorous acid (H3PO3)?

Answer 1

PCl3 + 3H2O --------> H3PO3 + 3HCl

stoichimetric masss

PCl3 = 1mole×137.33g/mol = 137.33g

H2O = 3mole × 18 g/mol = 54g

H3PO3 = 1mole × 82g/mol = 82g

HCl = 3mole × 36.46 =109.38g

Actual mass of reactants

PCl3 = 220g

water = excess

Theoretical yield

stoichiometrically 137.33g of PCl3 give 109.38g of HCl

therefore, 220g of PCl3 should give

(109.38g/137.33g)×220g =175.22g of HCl

so , theoretical yield = 175.22g

percent yield

percent yield = (actual yield/theoretical yield) × 100

= (122g/175.22g)×100

= 69.63%