What mass of DDT is formed, assuming 100% yield?

Question

DDT, an insecticide harmful to fish, birds, and humans, is produced by the following reaction.

2 C6H5Cl	+	C2HOCl3	→	C14H9Cl5	+	H2O
chlorobenzene		chloral		DDT

In a government lab, 477.8 g of chlorobenzene is reacted with 514 g of chloral.

(a)What mass of DDT is formed, assuming 100% yield?

(b) Which reactant is limiting? Which is in excess?

(c) What mass of the excess reactant is left over?

(d) If the actual yield of DDT is 206.2 g, what is the percent yield?

Answer 1

2C₆H₅Cl + C₂HOCl₃ ===> C₁₄H₉Cl₅ + H₂O ... balanced equation

moles chlorobenzene = 477.8 g x 1 mol/112.6 g = 4.243 moles

moles chloral = 514 g x 1 mol/147.4 g = 3.487 moles

Limiting reactant = chlorobenzene (requires 2 moles for each mole chloral)

(a) Theoretical yield DDT: 4.243 mol chlorbenzene x 1 mol DDT/2 mol chlorbenzene x 354.5 g/mol = 752.1 g

(b) Chlorobenzene is limiting; chloral is in excess

(c) 4.243 mol chlorobenzene x 1 mol chloral/2 mol chlorobenzene = 2.122 mol chloral used up. 3.487 mol - 2.122 mol = 1.365 mol chloral left x 147.4 g/mol = 201.2 g chloral left over.

(d) Percent yield = actual yield/theoretical yield (x100%) = 206.2 g/752.1 g (x100%) = 27.42%