# Chemistry Help! Exam tomorrow.

#### JohnDoeDDS

##### Senior Member
10+ Year Member
7+ Year Member
Well guys I have another chem question. I have an exam tomorrow and I can't seem to figure out how to do this problem. I would really appreciate some help ASAP, thanks. Here it is:

When 2.674g of ethane (CH3CH3) reacts with 8.845g of chlorine gas (Cl2) to produce hexachloroethane (CCl3CCl3) (a) What's the limiting re-agent? (b) What is the theoretical yield of chloromethane?

CH3CH3+ 3Cl2 ---> CCl3CCl3
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Okay now I got that the limiting reagent is Cl2. Now what? How do I calcualte the theoretical yield? Let alone chloromethane! The book Im using is very vague on this and I am having some trouble understanding this. I would really appreciate some help. Thanks guys.

#### psiyung

##### 1K Member
10+ Year Member
the theoretical yield basically shows you that in a 'perfect' laboratory situation, the maximal amount of product that can be formed is X, based on the standards of the limiting reagent.

Now, since you found the limiting reagent (in this case Cl2) you must have found the theoretical yield.

8.845g of Cl2 *1 mol/71g * 1 mol/3 mol* 95 g of product/1 mol = 3.77 grams. This should be your theoretical yield (if I did the calculation correctly).

The % yield = actual yield (which is usually given in the problem) / theoretical yield

the answer X 100 is the % yield. So if they ask you for % yield, they might state in the problem that you recovered 2.4 grams of the product

OP
J

#### JohnDoeDDS

##### Senior Member
10+ Year Member
7+ Year Member
psiyung said:
the theoretical yield basically shows you that in a 'perfect' laboratory situation, the maximal amount of product that can be formed is X, based on the standards of the limiting reagent.

Now, since you found the limiting reagent (in this case Cl2) you must have found the theoretical yield.

8.845g of Cl2 *1 mol/71g * 1 mol/3 mol* 95 g of product/1 mol = 3.77 grams. This should be your theoretical yield (if I did the calculation correctly).

The % yield = actual yield (which is usually given in the problem) / theoretical yield

the answer X 100 is the % yield. So if they ask you for % yield, they might state in the problem that you recovered 2.4 grams of the product