Final answer:
The enthalpy change for the reaction can be determined by calculating the difference in enthalpies of formation between the reactants and products.
Step-by-step explanation:
The enthalpy change for the reaction: 2H₂(g) + N₂(g) → 2HCN(g) can be determined by looking at the enthalpies of formation of the reactants and products.
The enthalpy change for the reaction can be calculated using the formula: ∆H = ∑(∆Hf(products)) - ∑(∆Hf(reactants)).
If the enthalpy change is negative, the reaction is exothermic. If the enthalpy change is positive, the reaction is endothermic.
In this case, you would need to know the enthalpies of formation for H₂(g), N₂(g), and HCN(g) to calculate the enthalpy change.