2c(s) + 2h2(g) → c2h4(g): δh = +52.4 kj/mol
which statement about this reaction is correct?

Answer;

26.2 kJ of energy are absorbed for every mole of carbon reacted

Explanation;ΔH is the enthalpy change which is given by subtracting the energy of reactants from the energy of products.That is; ΔH = energy of products - energy of reactantsIn this case, it means that C2H4 has more energy than the the reactants. 52.4 J of energy to be precise, this energy is absorbed during the reaction.However, Two moles of Carbon  require that much energy, thus one mole will require only 26.2 to react.

D)can be increased in a closed system