8. Thermochemistry

Calculate the ∆Hrxn for the following thermochemical equation: 

When given the following: 

Calculate the ∆H_rxn for 

Given the following set of reactions: 

Calculate the ∆H_rxn for 

Given the following reactions:

N₂ + 2 O₂ → 2 NO₂
Based on the following data.
2 NO → N₂ + O₂    ΔH = −180 kJ
2 NO + O₂ → 2 NO₂    ΔH = −112 kJ

Calculate the enthalpy of the reaction 4B(s) + 3O₂(g) → 2B₂O₃(s)

Calculate the enthalpy of the reaction 4B(s) + 3O₂(g) → 2B₂O₃(s).

Consider the reaction H2O(l) → H2O(g), ΔH =44.0 kJ what will ΔH be for the reaction if it is reversed?

You are given the following hypothetical reactions:

2 A → B + C     ΔH = +50 kJ  

A → D          ΔH = −80 kJ

a. Use Hess’s law to calculate ΔH for the reaction B + C → 2 D.

b. What is ΔH for the reaction D → ½ B + ½ C?

Dimethyl ether, CH₃OCH₃(𝑔), is an industrially useful organic compound that is a gas at room temperature. Consider the following balanced thermochemical equations:

CH₃OCH₃(g) + 3 O₂(g) → 2 CO₂(g) + 3 H₂O(g) ΔH° = −1328 kJ          

CH₄(g) + 2 O₂(g) → CO₂(g) + 2 H₂O(g) ΔH° = −802 kJ      

2 C₂H₆(g) + 7 O₂(g) → 4 CO₂(g) + 6 H₂O(g) ΔH° = −2855 kJ

a. All three of the above reactions produce H2O(𝑔). If they were written to produce H2O(𝑙) instead, would the values of Δ𝐻° become more negative, become less negative, or stay the same?

b. By using Hess’s law and the reactions provided, calculate Δ𝐻° for the following balanced reaction between dimethyl ether and methane to produce ethane and water:

CH₃OCH₃(g) + 2 CH₄(g) → 2 C₂H₆(g) + H₂O(g)