1. No category

Kings High School • AP Chemistry
Name _________________________________
Period ___ Date ___/___/___
8 • Bonding & Molecular Structure
H
C
N
O
F
Si
P
S
Cl
Br
I
Table 9.9 • Some Average SingleH
C
N
O
F
436
413
391
463
565
346
305
358
485
163
201
283
146
155
BOND ENERG
and Multiple-Bond Energies (kJ/mol)
Si
P
S
Cl
Br
318
322
347
432
366
272
339
285
192
452
335
218
201
565
490
284
253
249
222
293
381
310
201
326
226
255
242
216
193
Multiple Bonds
N=N
418
C=C
945
N≡N
C≡C
C=N
615
C=O*
887
C≡N
C≡O
O=O (in O2) 498
*C=O (in CO2)
IES
I
299
213
201
278
234
184
208
175
151
602
835
732
1072
799
1. Write the balanced equation for the combustion of 1 mole of ethane, CH4(g), forming H2O(l).
2. Draw the shortcut Lewis structures (use dashes instead of dots) for each of the molecules involved.
CH4
O2
CO2
H2 O
3. Calculate the bond energies of the reactants.
__ C−H
__ C−C
__ O=O
@ _________ kJ/mol = ____________
@ _________ kJ/mol = ____________
@ _________ kJ/mol = ____________
Total Bond Energy (Reactants) =
Calculate the bond energies of the products.
__ C=O
__ O−H
@ _________ kJ/mol = ____________
@ _________ kJ/mol = ____________
Total Bond Energy (Products) =
4. ΔHreaction = Bond Energy(reactants) – Bond Energy(products)
What is the ΔHcombustion based on bond energies? ____________
5.
(This question comes from an old FRQ test)
Average Bond Dissociation
Energies at 298 K
Bond
Bond Energy, kJ mol-1
414
C−H
347
C−C
377
C−Cl
243
Cl−Cl
431
H−Cl
(a)
6.
C2H5Cl(g) + Cl2(g) → C2H4Cl2(g) + HCl(g)
Calculate the ΔH° for the reaction above, using the table of average bond dissociation energies.
When ethanol (shown below) burns in air, heat is released. Estimate the enthalpy of combustion of
ethanol vapor ΔH° from the average bond energies.