
Concept explainers
DDT, an insecticide harmful to fish, birds, and humans,is produced by the following reaction:
In a government lab, 1142 g of chlorobenzene is reactedwith 485 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 200.0 g, what is thepercent yield?
(a)

Interpretation: The mass of DDT formed, assuming
Concept introduction: The limiting reactant is the reactant which depleted completely in a reaction and the amount of the product formed is also depends upon this. The excess reactant is the reactant which does not reacted completely in a reaction and some of the amount of such reactant left unreacted.
Answer to Problem 86E
The mass of DDT formed, assuming
Explanation of Solution
The given balanced chemical equation is given below.
The given mass of
The given mass of chloral,
The standard molar mass of
The standard molar mass of
The standard molar mass of
The formula to compute number of moles is as follows.
Substitute the values of given mass and molar mass of
Substitute the values of given mass and molar mass of
From the balanced equation, it is clear that
So,
But, only
So,
Thus, amount of product formed depends on amount of chloral.
One mole of chloral produces one mole of DDT.
So,
The formula to calculate the mass of a substance is as follows.
Substitute the molar mass and moles of DDT in equation (2).
Therefore, the mass of DDT formed, assuming
(b)

Interpretation: The limiting reactant and excess reactant are to be predicted.
Concept introduction: The limiting reactant is the reactant which depleted completely in a reaction and the amount of the product formed is also depends upon this. The excess reactant is the reactant which does not reacted completely in a reaction and some of the amount of such reactant left unreacted.
Answer to Problem 86E
The limiting reactant is
Explanation of Solution
The given balanced chemical equation is given below.
The given mass of
The given mass of chloral,
The standard molar mass of
The standard molar mass of
The formula to compute number of moles is as follows.
Substitute the values of given mass and molar mass of
So, moles of
Substitute the value of given mass and molar mass of
From the balanced equation, it is clear that
So,
But, only
So,
Therefore, the limiting reactant is
(c)

Interpretation: The mass of excess reactant that is left is to be calculated.
Concept introduction: The limiting reactant is the reactant which depleted completely in a reaction and the amount of the product formed is also depends upon this. The excess reactant is the reactant which does not reacted completely in a reaction and some of the amount of such reactant left unreacted.
Answer to Problem 86E
The mass of excess reactant left is
Explanation of Solution
The given balanced chemical equation is given below.
The given mass of
The given mass of chloral,
The standard molar mass of
The standard molar mass of
The given mass of
The formula to compute number of moles is as follows.
Substitute the value of given mass and molar mass of
Substitute the value of given mass and molar mass of
From the balanced equation, it is clear that
So, the
But, only
So, the reactant present in excess amount is
The formula to calculate the left amount of excess reactant using number of moles is as follows.
Substitute the initial moles and reacted moles of
Therefore, the mass of excess reactant left is
(d)

Interpretation: The percent yield of DDT is to be calculated.
Concept introduction: The percent yield of a substance is calculated by using actual yield and theoretical yield. The formula to calculate the percent yield is shown below.
Answer to Problem 86E
The percent yield of DDT is
Explanation of Solution
The given balanced chemical equation is given below.
The given actual yield of DDT is
The calculated or theoretical yield of DDT is
The formula to calculate the percent yield is as follows.
Substitute the values of actual yield and theoretical yield of DDT in equation (4).
Therefore, the percent yield of DDT is
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Chapter 3 Solutions
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