CHEM 1A: Challenge Problem Set 14
1. Copper (I) oxide can be oxidized to copper (II) oxide by the following equation:
2 Cu2O(s) + O2(g) → 4 CuO(s)
ΔH°rxn = -292.0 kJ
Given the enthalpy of formation of Cu2O(s) is -168.6 kJ/mol, calculate the ΔH°formation of CuO(s) (in kJ/mol).
2. If the gas phase reaction below is EXOTHERMIC, which of the following statements is true? Mark all that
apply.
HCl(g) + CH3(g) → Cl(g) + CH4(g)
A. a C--C bond is weaker than a H--Cl bond.
B. a C--H bond is weaker than a H--Cl bond.
C. a C--H bond is stronger than a H--Cl bond.
D. a C--Cl bond is stronger than a C--C bond.
E. The reaction absorbs heat.
3. Consider the reaction below:
2 HCl(aq) + Ba(OH)2(aq) → BaCl2(aq) + 2 H2O(l)
ΔH°rxn = -118 kJ
Calculate the heat of the reaction (qreaction in kJ) if 900.0 mL of 1.500 M Ba(OH)2 solution is mixed with 600.0
mL of 2.50 M HCl solution.
Hint: Consider the limiting reagent, if applicable.
4. Using ONLY the information available below, calculate the approximate bond dissociation energy of the
triple bond (C≡O) in carbon monoxide, in kJ/mol.
2 CO(g) + 2 H2O(g) → 2 CO2(g) + 2 H2(g)
ΔHrxn = -82 kJ
Average Bond Dissociation Energies (BDE) in kJ/mol:
C—O: 358
H—O: 467
C=O: 799
O—O: 204
H—H: 432
O=O: 498
C—H: 413
C—C: 347
C=C: 614
C≡C: 839
5. Use the chemical transformations below in combination with the corresponding enthalpies of reactions to
calculate the MOLAR enthalpy of decomposition of solid ammonium nitrate to nitrogen gas, oxygen
gas and water vapor (in kJ/mol).
HINT: The molar enthalpy of decomposition refers to the enthalpy change when 1 MOLE of ammonium nitrate
decomposes.
1/2 N2(g) + 3/2 H2(g) → NH3(g)
ΔHF = -46 kJ/mol
1/2 H2(g) + 1/2 N2(g) + 3/2 O2(g) → HNO3(aq)
ΔHF = -206.0 kJ/mol
NH4NO3(s) → NH4NO3(aq)
ΔHdissolution = 25.7 kJ/mol
H2O(l) → H2O(g)
ΔHvap. = 44.0 kJ/mol
NH3(g) + HNO3(aq) → NH4NO3(aq)
ΔHneut. = -86.5 kJ/mol
H2(g) + 1/2 O2(g) → H2O(l)
ΔHF = -285.8 kJ/mol