Question

DDT is an insecticide banned by the U. S. government because of its hazard to fish and birds. It can be prepared as follows: 2 C6H5Cl + C2HOCl3  C14H9Cl5 + H2O chlorobenzene chloral DDT If 451 g of chlorobenzene reacts with 368 g of chloral to yield 507 g of DDT, determine which species is the limiting reactant and calculate the theoretical yield and the percentage yield.

Answer 1

Molecular weights : Chlorobenzene= 112.5 chloral = 147, DDT = 354.5

moles : ChloroBenzene = 451/112.5=4.00      Chloral = 368/147=2.5

From the stoichiometry, 2 mole sof ChloroBenzne reacts with 1 mole of Chloral

Molar ratio = 2:1 Actural ratio = 4:2.5= 1.6 ;1

Since Chlorobenzene required is 2 and only one 1,6 moles of it is supplied, it is the limiting reactants

Moles of DDT fromed from the reaction = 4/2 =2 ( half the moles of limiting reactant)

Mass of DDT= 2*354.5= 709 gm

Theoretical yield =709 gm

Percent yield= 100* actual yield/ theoretical yield.

Percent yield = 100*507/709=71.5%