Question

Click on the Delta H changes sign whan a process is reversed button within the activity and analyze the relationship between the two reactions that are displayed. The reaction that was on the screen when you started and its derivative demonstrate that the reaction enthalpy, ΔH, changes sign when a process is reversed. Consider the reaction B(s)+32O2(g)→B2O3(s), ΔH =−1270kJ What will ΔH be for the reaction if it is reversed?

Answer 1

Answer:

ΔH = 1270kJ

Explanation:

Let's consider the following thermochemical equation.

B(s) + 3/2 O₂(g) → B₂O₃(s), ΔH = −1270kJ

Since ΔH < 0, this reaction is exothermic. According to the Lavoisier-Laplace law, if we reverse a reaction, its enthalpy will have the same value and opposite sign than the direct reaction.

B₂O₃(s) → B(s) + 3/2 O₂(g), ΔH = 1270kJ

For the inverse reaction, ΔH > 0, which means that it is endothermic.