Question

How much heat is released if 2.00 moles
CF2Cl2 reacts with 70.0 g F2 with a 75.0
percent yield?
CF2Cl2 + F2 ! CF4 + Cl2

H for this reaction is -401 kJ/mol rxn.
1. 553 kJ
2. 739 kJ
3. 985 kJ
4. 601 kJ
5. 1069 kJ
6. 802 kJ

Answer 1

First determine which is the limiting reagent. Use that to determine how much of the CF2Cl2 is used for 100% yield. Then 401 kJ/mol x mols CF2Cl2 use = kJ produced for 100% yield.
kJ produced x 0.75 = heat produced with 75% yield. This assumes that other reactions producing heat do not occur.

Answer 2

Answer 1; 553 kJ