Use average bond energies together with the standard enthalpy of formation of C( g) (718.4 kJ/mol) to estimate the standard enthalpy of formation of gaseous benzene, C6H6( g). (Remember that average bond energies apply to the gas phase only.) Compare the value you obtain using average bond energies to the actual standard enthalpy of formation of gaseous benzene,82.9 kJ/mol. What does the difference between these two values tell you about the stability of benzene?

3. Write out the chemical equation for the enthalpy of formation of NaCl(s).

Methanol can be synthesized from graphite according to the following reaction, calculate the enthalpy change, in kJ/mol, for the overall reaction: 2C(graphite) + 4H2(g) + O2(g) → 2CH3OH(l) Using the data given below: C(graphite) + O2(g) → CO2(g)     ΔrH = -393.5 kJ/mol 2H2(g) + O2(g) → 2H2O(l)     ΔrH = -571.6 kJ/mol 2CH3OH(l) + 3O2(g) → 2CO2(g) + 4H2O(l)     ΔrH = -1452.8 kJ/mol (Enter the numerical value in the space provided below, be sure to include the negative sign if needed.

23.

Use the molar bond enthalpy data in the table to estimate the value of Δ?∘rxn for the equation   NH3(g)+2O2(g)⟶HNO3(g)+H2O(g)

3. A 10.0 g sample of pure acetic acid, CH3CO2H, is completely burned. The heat released warms 2.0 L of water from 22.3°C to 39.6°C. a. Assuming that no heat was lost to the calorimeter, what is the molar enthalpy change of the complete combustion of acetic acid? Express your answer in kJ/mol.I b. Will the bonds in the products be longer or shorter than the bonds in the reactant

5. For the chemical reaction below (please note, this is the same as CH4 + Br2 → CH3Br + HBr; the Br2 over the arrow is a reactant. Let me know if you have any questions about this): a. How many non-polar and polar bonds are in the reactants? b. How many non-polar and polar bonds are in the products? c. What is the change in enthalpy (AH) for this reaction (positive or negative)? What is the evidence for your response? d. What is the change in entropy (AS) for this reaction (positive or negative)? What is your evidence for your response? e. Is this reaction exergonic (spontaneous) or endergonic (nonspontaneous)? f. Is the carbon in this reaction being reduced or oxidized? What evidence do you have for your claim? H H-CH- H Br₂ hv H H-C-Br + -Br + HBr H

2. Using Hess's Law, Calculate enthalpy change for: NO (g) + O₂ (g) → NO₂ (g) Given the following enthalpies of reaction ½ N₂ (g) + O₂(g) → NO₂(g) AH = + 33.8 kJ 12 N₂ (g) + 1/2O2 → NO (g) AH = -566.0 kJ

Ammonia reacts with oxygen to form nitrogen dioxide and steam, as follows: 4 NH3 (g) + 7 O2 (g) → 4 NO2 (g) + 6 H2O (g) Calculate the enthalpy change of the reaction.

What is the assumption made when chemical reactions are performed which allows us to use enthalpy, ΔH, instead of energy, ΔE?