Chemistry · THERMODYNAMICS

Consider the following chemical reactions and statements regarding \( \Delta H \) and \( \Delta U \) at constant temperature: (A) For the reaction \( \text{C}(s) + \text{O}_2(g) \rightarrow \text{CO}_2(g) \), \( \Delta n_g = 0 \), therefore \( \Delta H = \Delta U \). (B) For the reaction \( \text{N}_2(g) + 3\text{H}_2(g) \rightarrow 2\text{NH}_3(g) \), \( \Delta n_g = -2 \), therefore \( \Delta H < \Delta U \). (C) For the reaction \( \text{PCl}_5(g) \rightarrow \text{PCl}_3(g) + \text{Cl}_2(g) \), \( \Delta n_g = +1 \), therefore \( \Delta H > \Delta U \). (D) For an isochoric process with no non-expansion work, \( \Delta U = q_v \). How many of the above statements are correct?

1. A
   Only one
2. B
   Only two
3. C
   Only three
4. D
   All four