Answer:
= 238.6J
Explanation:
According to the law of conservation of energy, energy can neither be created nor be destroyed. It can only be transformed from one form to another.
Endothermic reactions are those in which heat is absorbed by the system and thus the energy of products is higher than the energy of reactants.
For the given reaction:
A + B ⇄ C + D
Energy of A = 85.1 J
Energy of B = 87.9 J
Product C contains 38.7 J
Energy balance:
∑ enthalpy of the reactants + energy added = ∑ enthalpy of the products + energy released.
∑ enthalpy of the reactants = 85.1 J + 87.9 J = 173 J
energy added = 104.3 J
∑ enthalpy of the products = 38.7 J + D
energy released = 0
Equation:
173J + 104.3J = 38.7 + D + 0
⇒ D = 173J + 104.3J - 38.7J
= 238.6J
which is the chemical energy of the product D