Using values from Appendix C in your textbook, calculate the value of ΔH° for the reaction

4 NH3(g) + 5 O2(g) → 4 NO(g) + 6 H2O(g)

To calculate the value of ΔH° for the reaction, we need to use Hess's Law and the given standard enthalpy of formation values from Appendix C of your textbook.

Hess's Law states that if a reactant is converted to a product through multiple steps, then the overall change in enthalpy for the reaction is the sum of the enthalpy changes for each step.

Here's how you can calculate ΔH° for the given reaction:

1. Write down the balanced chemical equation:
4 NH3(g) + 5 O2(g) → 4 NO(g) + 6 H2O(g)

2. Break down the given reaction into simpler steps with known enthalpies:
i. 4 NH3(g) → 4 N(g) + 12 H(g) (given in Appendix C)
ii. 5/2 O2(g) → 5 O(g) (given in Appendix C)
iii. 4 N(g) + 5 O(g) → 4 NO(g) (given in Appendix C)
iv. 12 H(g) + 5 O(g) → 6 H2O(g) (given in Appendix C)

3. Add up the enthalpy changes for each step:
ΔH° = ΔH°f (4 NO(g)) + ΔH°f (6 H2O(g)) - ΔH°f (4 NH3(g)) - ΔH°f (5 O2(g))

4. Substitute the values from Appendix C:
ΔH° = [4(-90.3) + 6(-241.8) - 4(-45.9) - 5(0)] kJ/mol

5. Simplify the equation:
ΔH° = -360.0 kJ/mol + (-1450.8 kJ/mol) + 183.6 kJ/mol

6. Calculate the final value:
ΔH° = -360.0 kJ/mol - 1450.8 kJ/mol + 183.6 kJ/mol
= -1627.2 kJ/mol

Therefore, the value of ΔH° for the reaction is -1627.2 kJ/mol.