DDT, an insecticide harmful to fish, birds, and humans, is produced by the follo

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, 444.8 g of chlorobenzene is reacted with 509 g of chloral.
(a) What mass of DDT is formed, assuming 100% yield?
g

(b) Which reactant is limiting?
C6H5ClC2HOCl3    neither reactant is limiting [Correct: Your answer is correct.]
Which is in excess?
C6H5ClC2HOCl3    neither reactant is in excess [Correct: Your answer is correct.]
(c) What mass of the excess reactant is left over?
g

(d) If the actual yield of DDT is 205.7 g, what is the percent yield?
%

Explanation / Answer

(a) 2 C6H5Cl + C2HOCl3 C14H9Cl5 + H2O

According to the reaction 2 moles of chlorobenzene reacts with 1 mole of chloral to produce 1 mole of DDT

Number of moles of C6H5Cl = mass given / molecular mass = 444.8 / 112.56 = 3.95 moles

Number of moles of C2HOCl3 = 509 / 147.388 = 3.45 moles

Number of moles of chlorobenzene required to react with 3.45 moles of chloral = 2 x 3.45 = 6.9 moles

3.95 moles of chlorobenzene can react with only 1.97 moles of chloral giving, 1.97 moles of DDT

Mass of DDT produced = number of moles x molecular mass = 1.97 x 354.49 = 698.35 g

(b) Since not enough chlorobenzene is present to react with given mass of chloral, therefore chlorobenzene is the limiting reagent.

(c) Choral left after reaction = 3.45 - 1.97 = 1.48 moles

Mass left = 1.48 x 147.388 = 218.134 g

(d) Percent yield = (Actual yield / Theoretical yield) x 100 = (205.7 /698.35 g) x 100 = 29.45 %

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