Final answer:
For the reverse chemical reaction c 3d → a 2b, the value of ΔH would be -170 kJ, reflecting the reversal of energy exchange from the original reaction.
Step-by-step explanation:
The question asks to determine the value of ΔH for the reverse reaction c 3d → a 2b, given the reaction a 2b → c 3d has a ΔH of 170 kJ. When a chemical reaction is reversed, the sign of the enthalpy change (ΔH) is also reversed. Therefore, for the reverse reaction c 3d → a 2b, the value of ΔH would be -170 kJ. This is because the process of forming bonds releases energy, while breaking bonds requires energy; hence, when a reaction is reversed, the energy exchange is also reversed.